So this is right:
^There are too many apples :) Correct me if I'm wrong with this, I haven't done maths for ages!
Okay, let x = total number of apples.
x/5 + x/3 + x/6 = x - 18
Basically, the addition of 1/5, 1/3 and 1/6 of the total number of apples will equal the apples that have been...