Show and hide text in several elements of the same class

Welcome to the community.

"getElementByClassName" returns an array with all the elements of that calse, so to edit them, you must go through that array.

Try something like this

var x = document.getElementsByClassName('info-mas');

for (var i = 0; i < x.length; i++) {
  x[i].style.display= "none";
}

I also recommend that when you ask a question, publish your code as text and not as an image; so we can help you easier.

I hope you serve, you can see an example here link