When Eva was 39 years old, her daughter was 3 times her son's age. Eva would be twice her daughter's age when her son was 29 years old. How old would Eva be when her son was 17 years old?

	Eva	Daughter	Son
Before	39	3 u	1 u
Change	+ ?	+ ?	+ ?
After	2 p	1 p	29

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

Difference in Eva's and her daughter's ages at first
39 - 3 u = 2 p - 1 p
39 - 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 - 29
2 u + 29 = 1 p --- (2)

Make p the same.

(1) = (2)
39 - 3 u = 2 u + 29
2 u + 3 u = 39 - 29
5 u = 10

1 u = 10 ÷ 5 = 2

Age difference between Eva and her son
= 39 - 1 u
= 39 - 2
= 37

Eva's age when her son was 17 years old
= 37 + 17
= 54

Answer(s): 54