When Risa was 38 years old, her daughter was 3 times her son's age. Risa would be twice her daughter's age when her son was 23 years old. How old would Risa be when her son was 5 years old?

	Risa	Daughter	Son
Before	38	3 u	1 u
Change	+ ?	+ ?	+ ?
After	2 p	1 p	23

The difference in the ages between Risa and her daughter remains unchanged.

Difference in Risa's and her daughter's ages at first
38 - 3 u = 2 p - 1 p
38 - 3 u = 1 p --- (1)

The difference in the ages between her daughter and her son remains unchanged.

Difference in her daughter's and her son's ages at first
3 u - 1 u = 1 p - 23
2 u + 23 = 1 p --- (2)

Make p the same.

(1) = (2)
38 - 3 u = 2 u + 23
2 u + 3 u = 38 - 23
5 u = 15

1 u = 15 ÷ 5 = 3

Age difference between Risa and her son
= 38 - 1 u
= 38 - 3
= 35

Risa's age when her son was 5 years old
= 35 + 5
= 40

Answer(s): 40