I have an error in the AdminSQLiteOpenHelper and in the getWritableDatabase

// this is from the bd package com.example.manuu.basededatos3;

import android.content.ContentValues; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase; import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.view.View; import android.widget.Button; import android.widget.EditText; import android.widget.RadioButton; import android.widget.TextView; import android.widget.Toast;

public class MainActivity extends AppCompatActivity {     EditText nom, surname, nocontrol, calif1, calif2, calif3;     TextView prom;     Button calcu, high, low, modifi, consul;     RadioButton apro, repro;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    nom = (EditText) findViewById(R.id.nom);
    apellidos = (EditText) findViewById(R.id.apellidos);
    nocontrol = (EditText) findViewById(R.id.nocontrol);
    calif1 = (EditText) findViewById(R.id.calif1);
    calif2 = (EditText) findViewById(R.id.calif2);
    calif3 = (EditText) findViewById(R.id.calif3);


    prom = (TextView) findViewById(R.id.prom);

    calcu = (Button) findViewById(R.id.calcu);
    alta = (Button) findViewById(R.id.alta);
    baja = (Button) findViewById(R.id.baja);
    modifi = (Button) findViewById(R.id.modifi);
    consul = (Button) findViewById(R.id.consul);


    apro = (RadioButton) findViewById(R.id.apro);
    repro = (RadioButton) findViewById(R.id.repro);

}

public void alta(View view) {
    Bd admin = new Bd(this, "administracion", null, 1);
    SQLiteDatabase bd = admin.getWritableDatabase();
    String nombre = nom.getText().toString();
    String ape = apellidos.getText().toString();
    String noC = nocontrol.getText().toString();
    int cal = Integer.parseInt(calif1.getText().toString());
    int cal2 = Integer.parseInt(calif2.getText().toString());
    int cal3 = Integer.parseInt(calif3.getText().toString());
    int pro = Integer.parseInt(prom.getText().toString());
    ContentValues registro = new ContentValues();
    registro.put("nombres", nombre);
    registro.put("apellidos", ape);
    registro.put("Numero de control", noC);
    registro.put("Calificación 1", cal);
    registro.put("Calificación 2", cal2);
    registro.put("Calificación 3", cal3);
    registro.put("pro", pro);
    bd.insert("Alumnos", null, registro);
    bd.close();
    nom.setText("");
    apellidos.setText("");
    nocontrol.setText("");
    calif1.setText("");
    calif2.setText("");
    calif3.setText("");
    prom.setText("");
    Toast.makeText(this, "Se cargaron todos los datos del alumno", Toast.LENGTH_SHORT).show();
}

public void consultapornumerodecontrol(View v) {

    AdminSQLiteOpenHelper admin = new AdminSQLiteOpenHelper(this, "administracion", null, 1);
    SQLiteDatabase bd = admin.getWritableDatabase();
    String noC = nocontrol.getText().toString();
    Cursor fila = bd.rawQuery("select nombres,apellidos, nocontro,calif1,calif2,calif3,prom from Alumnos where codigo=" + cod, null);
    if (fila.moveToFirst()) {
        nom.setText(fila.getString(0));
        apellidos.setText(fila.getString(1));
        nocontrol.setText(fila.getString(2));
        calif1.setText(fila.getString(3));
        calif2.setText(fila.getString(4));
        calif3.setText(fila.getString(5));
        prom.setText(fila.getString(6));
    } else
        Toast.makeText(this, "No existe alumno con dicho numero de control", Toast.LENGTH_SHORT).show();
    bd.close();
}

public void bajapornocoltrol(View v) {
    AdminSQLiteOpenHelper admin = new AdminSQLiteOpenHelper(this, "administracion", null, 1);
    SQLiteDatabase bd = admin.getWritableDatabase();
    String noC = nocontrol.getText().toString();
    int cant = bd.delete("Alumnos"."codigo=" + cod, null);
    bd.close();
    nom.setText("");
    apellidos.setText("");
    nocontrol.setText("");
    calif1.setText("");
    calif2.setText("");
    calif3.setText("");
    prom.setText("");
    if (cant == 1)
        Toast.makeText(this, "Se borro el alumno con dicho codigo", Toast.LENGTH_SHORT).show();
    else
        Toast.makeText(this, "No existe alumno con dicho numero de control", Toast.LENGTH_SHORT).show();
}

public void modificacion(View v) {
    AdminSQLiteOpenHelper admin = new AdminSQLiteOpenHelper(this, "administracion", null, 1);
    SQLiteDatabase bd = admin.getWritableDatabase();
    String noC = nocontrol.getText().toString();
    String nombre = nom.getText().toString();
    String ape = apellidos.getText().toString();
    String cal3 = calif3.getText().toString();
    String cal2 = calif2.getText().toString();
    String cal = calif1.getText().toString();
    String pro = prom.getText().toString();
    ContentValues registro = new ContentValues();
    registro.put("numero de control", noC);
    registro.put("nombre", nombre);
    registro.put("apellidos", ape);
    registro.put("calificacion 1", cal);
    registro.put("calificacion 2", cal2);
    registro.put("calificacion 3", cal3);
    registro.put("promedio", pro);
    int cant = bd.delete("Alumnos"."codigo=" + cod, null);
    bd.close();
    if (cant == 1)
        Toast.makeText(this, "Se modificaron los datos", Toast.LENGTH_SHORT).show();
    else
        Toast.makeText(this, "No existe alumno con dicho numero de control", Toast.LENGTH_SHORT).show();


}

} // this is from the activityMain

package com.example.manuu.basededatos3;

import android.content.Context; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteOpenHelper;

public class Bd extends SQLiteOpenHelper {     public Bd (Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {         super (context, name, factory, version);     }

@Override
public void onCreate(SQLiteDatabase db) {
    db.execSQL("create table Alumnos(NoControl Integer primary key, nombre text, apeliidos text, promedio int)");

}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

}

} // this is from the file in the bd