Question 5 - A-Level Maths

In this question you must show detailed reasoning.
1. Given that $x$ and $y$ are positive numbers such that
$$( x - y ) ^ { 3 } > x ^ { 3 } - y ^ { 3 }$$ prove that $$y > x$$
Using a counter example, show that the result in part (a) is not true for all real numbers.