Question: Boris has 100 apples. Beck has 23 fewer apples than Boris. If Boris gives Beck 10 apples, how many fewer apples does Beck have than Boris now?
Solve it. 
Answer: 
Boris has 100 apples, but gives 10 away, so now he has 100 apples - 10 apples = 90 apples.
Beck has 23 fewer than Boris at the start, so he started with 100 - 23 = 77 apples.
However, since he gets 10 from Boris, he now has 77 apples + 10 apples = 87 apples.
Thus Beck has 90 - 87 = 3 apples fewer than Boris.