Answer :
20/5=4 (to find a fifth of 20 apples)
4x2=8 (to find what 2 fifths is)
He used 8 apples
4x2=8 (to find what 2 fifths is)
He used 8 apples
The best way to do this one is by multiplication. If you have two dozens of eggs, you multiply two by a dozen to find out how many eggs you have: 2*12=24. Similarly, if you have two fifths of 20 apples, you multiply 2/5 by 20 to find out how many apples you have: (2/5)*20 = 8.