Explanation:
so, what's the problem ?
it's all there, we only need to take the calculator (or simply our heads) and do the calculation :
2×5 - 5×2 = 10 - 10 = 0
you see ? that was all that was needed.
put the given values for the variables into the places of these variables, and then calculate !
that is what variables are for : placeholders for actual values.