Thank you teacher!

Explanation and method is correct BUT there was careless mistake where question says 5:2 but working wrote 5:3 , as well as there working showing 75 : 45 but used 42 instead when minusing :(

Using same method, correct answer would be
5:2 —> 50:20 where diff is 30
so take any of their CURRENT age ( S: 42 or D: 12 )
And minus it from the supposed age , either
50-42=8 or 20-12=8

So answer would be in 8 years time. :D

Ooops, Thank you for point out the mistake.

Thank you for the correction!
I got the concept.