Answer:
son = 18 years old.
Step-by-step explanation:
Father to son = f/s = 7./3 Cross Multiply
3f = 7s
f + s = 60
f=60 - s
3(60-s)= 7s
180 - 3s = 7s
180 = 7s + 3s
180 = 10s
s = 180/10
s = 18
