Question

A boy is now twice as old as his sister, four years ago, he was thrice as old as her what are their ages now?

Answer 1

let boy age is X ,sister age =y
so according to statement
X=2Y---(1)

now four year ago
(X-4)=3(Y-4)
(X-4)=3Y-12
so as we know X=2Y then,
2Y-4=3Y-12
2Y+8=3Y
8=3Y-2Y
8=Y
so her sister age is now 8 year
and boy is twice of her age=2(8)=16 years
----hope it helps---