Write a function that would allow you to do this

multiply(5)(6);

You can create a closure to keep the value of a even after the inner function is returned. The inner function that is being returned is created within an outer function, making it a closure, and it has access to the variables within the outer function, in this case the variable a.

function multiply(a) {
  return function(b) {
    return a * b;
  }
}

multiply(5)(6);