Let’s define our variables:
D = dad’s age now
S = son’s age now
Given:
D=4S now
D+4=3(S+4) in 4 years
We can expand the second equation:
D+4=3S+12
D=3S+8
And we can subtract it from D=4S
D=4S-(D=3S+8)
0=S-8
S=8 the son’s age now.
D=4S=4(8)=32 the father’s age now
Check:
32+4=3(8+4)
36=3(12)
36=36 Check
I hope this helps you
