Hey there! I'm happy to help!
We see that the father is 60 years old, and the son is half of that age, so this means that the son is 30 years old.
We want to see the age the son was at when the father was four times his age. We know that the father is thirty years older than him, so we can write this equation with s representing the age of the son.
s+30=4s (30 years older than the son is equal to to four times the son's age at the time)
We subtract 30 from both sides.
s=4s-30
We subtract 4s from both sides.
-3s=-30
We divide both sides by -3.
s=10
Therefore, the boy was 10 when his father was four times his age. This is because his father would have been 40 because that is 30 more years than 10, and it is four times ten!
Have a wonderful day! :D
