When Eva was 36 years old, her daughter was 2 times her son's age. Eva would be twice her daughter's age when her son was 30 years old. How old would Eva be when her son was 8 years old?

	Eva	Daughter	Son
Before	36	2 u	1 u
Change	+ ?	+ ?	+ ?
After	2 p	1 p	30

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

Difference in Eva's and her daughter's ages at first
36 - 2 u = 2 p - 1 p
36 - 2 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
2 u - 1 u = 1 p - 30
1 u + 30 = 1 p --- (2)

Make p the same.

(1) = (2)
36 - 2 u = 1 u + 30
1 u + 2 u = 36 - 30
3 u = 6

1 u = 6 ÷ 3 = 2

Age difference between Eva and her son
= 36 - 1 u
= 36 - 2
= 34

Eva's age when her son was 8 years old
= 34 + 8
= 42

Answer(s): 42