Question

the difference of ages between 2 sisters is 10 years, 15 years ago elder 1 was twice as old as younger age. find the both present age?

Answer 1

b-a=10
(b-15) = 2(a-15)

(a+10-15) = 2(a-15)
a-5 = 2a-30
a = 25

So, the sisters are 25 and 35

check:
15 years ago they were 10 and 20