C = child's age
m = mother's age
C + 21 = m
5(c + 6) = m + 6
= 5c + 30 = m + 6
= 5c + 24 = m
5c + 24 = c+ 21
4c + 24 = 21
4c = - 3
c = -3/4
-3/4 + 21
= 20 1/4
m = 20 1/4
The child will be born in 9 months.
The mom is 20 years and 3 months old.
The mother is 20 years and 3 months old, and barely pregnant.