Here is the Math.max code in Chrome V8 engine.

function MathMax(arg1, arg2) {  // length == 2
  var length = %_ArgumentsLength();
  if (length == 2) {
    arg1 = TO_NUMBER(arg1);
    arg2 = TO_NUMBER(arg2);
    if (arg2 > arg1) return arg2;
    if (arg1 > arg2) return arg1;
    if (arg1 == arg2) {
      // Make sure -0 is considered less than +0.
      return (arg1 === 0 && %_IsMinusZero(arg1)) ? arg2 : arg1;
    }
    // All comparisons failed, one of the arguments must be NaN.
    return NaN;
  }
  var r = -INFINITY;
  for (var i = 0; i < length; i++) {
    var n = %_Arguments(i);
    n = TO_NUMBER(n);
    // Make sure +0 is considered greater than -0.
    if (NUMBER_IS_NAN(n) || n > r || (r === 0 && n === 0 && %_IsMinusZero(r))) {
      r = n;
    }
  }
  return r;
}

Here is the repository.

For this answer I will assume you have the answers put in an Array.

You can first use this function to find the max value of the array:

var maxValue = Math.max.apply(null, array);

Then you can find the amount of times this value occurs by using the following:

array.sort();
var nrOfMaxValue = array.lastIndexOf(maxValue) - array.indexOf(maxValue);

Hope this works for you!

edit: I just figured, if you only want to know if the max answer was given more than once you can just do this, without sorting the array:

var maxValue = Math.max.apply(null, array);
var onlyOnceAnswered = array.lastIndexOf(maxValue) == array.indexOf(maxValue);