Question

Ten years later, $A$ will be twice as old as $B$ and five years ago, $A$ was three times as old as $B$. What are the present ages of $B$?

Answer 1

Call A and B the 2 present ages.

Ten years from now, A is twice as old as B
(A + 10) = 2(B + 10)................ (1)

Five years ago, A was 3 times as old as B
(A - 5) = 3(B - 5) .....................(2).

Solve the system (1) and (2).
From (2) --> A = 3B - 15 + 5 = 3B - 10.

Replace this value of A into (1) -->
3B - 10 + 10 = 2B + 20
B = 20
Present age of B is20.