Question: the product of 15 and 4 less than a number is 240. what is the number?
Let N be the number. Then 4 less than the number is (N-4).
The product of 15 and 4 less than the number = 15*(N-4).
i.e. 15(N-4) = 240 -- divide both sides by 15, to give
(N-4) = 16 -- add 4 to both sides.
N = 20
Answer: the number is N = 20