Question

before 3 years the sum of father and two sons age was Y years, then after 2 years, the sum of their age will be

Answer 1

I think that the answer is (Y + 2) years. 

Hope this may help you. 

Answer 2

Present age =y +(3×2). ....... [As both father and son age is there]
Present age =y+6

Age after 2 years =y +6 +(2×2)
=y+10