Question 1141103

m = man's age
s = son's age
:
A man is three times as old as his son.
m = 3s
 Four years ago he was four times as old as his son was at that time.
m - 4 = 4(s - 4)
m - 4 = 4s - 16
m = 4s - 16 + 4
m = 4s - 12
:
 How old is the son
replace m with 3s
3s = 4s - 12
12 = 4s - 3s
 s = 12 yrs old is the son
:
:
Check solution in the statement:
m = 3(12) = 36
"Four years ago he was four times as old as his son was at that time. "
36 - 4 = 4(12 - 4)
32 = 4(8)