Simple math actionscript

I am hoping that someone can explian why this code doesn’t work.
var a = myNum.text;
var b = myNumb.text;
var c = myAnswer.text;
answer_btn.onRelease = function() {
if (c=a+b) {
trace(“ok”);
}
};
All the text boxes are set to input and I get no errors but no message in the output box
What I am trying to do is to be able to input numbers and then press a button to check your answer.