Answer:
20
Explanation:
In 12 years, the sum of their ages will be 24 more than it is now. The sum of their ages now is 61-24 = 37.
If Jennifer is 3 years older than Peter, we have ...
j + (j -3) = 37
2j = 40 . . . . . . add 3
j = 20 . . . . . . . divide by 2
Jennifer is now 20 years old.
_____
Peter is now 17 years old. In 12 years, they will be 29 and 32, so their ages will sum to 61.