mysql Queries with arithmetic operations

I have tried to find some kind of query that does arithmetic operations to show them in a table only the result. I've tried with count() but I only get the data and not the operations, such as adding and multiplying the sales.

For example, from sale 1 I have 3 different items get the summation and if I had more than 1 unit also multiplication, some subject that I recommend read to do so? so far I only achieve it by going through the vector that returns the query and doing the operations with php functions,

The query is normal:

SELECT * Fecha FROM 'ventas';

What is not done is how to make the summation of all the data. When I apply count and sum I only return the value of for example, sale 1 and not all sales.

The query that only returns my sales number but not the sum of the items sold, is where I'm stuck

SELECT NoVenta, COUNT(*) FROM ventas GROUP by NoVenta

<table>
  <tr>
    <th>No. Venta</th>
    <th>Total</th>
  </tr>
  <tr>
    <td>1</td>
    <td>550</td>
  </tr>
  <tr>
    <td>2</td>
    <td>700</td>
  </tr>
  <tr>
    <td>3</td>
    <td>800</td>
  </tr>
  <tr>
    <td>4</td>
    <td>900</td>
  </tr>
  <tr>
    <td>5</td>
    <td>600</td>
  </tr>
  <tr>
    <td>6</td>
    <td>500</td>
  </tr>
</table>