Given two integers a and x, return the minimum non-negative number to add to / subtract from a to make it a multiple of x.

We're adding or subtracting, not multiplying.

The kata is very confusing. The answer is always '0', as the easiest way to make 'a' the multiple of 'x' is 'a * x' thus '0' is the answer, and the whole kata makes no sense.

false is not false
true is not true

This is what I got. Such a nice kata

This task has really poorly written description, which lead you into wrong solution.