word problem using ages

[miller]

Matt is twice as old as his son. Twenty years ago, he was 4 times as old as his son was then. How old are they now?
Please help

 

[Denis]

Matt is twice as old as his son. 20 years ago, he was 4 times as old as his son was then. How old are they now?
Please help

S = son; so Matt = 2S : Matt is twice as old as his son

2S - 20 = 4(S - 20) : 20 years ago, he was 4 times as old as his son was then.

Carry on...