Riordan is 35 years older than his son. 10 years from now, his son will be ¹₂ of his age while his cousin will be ²₅ of his son. Express his cousin’s present age as a fraction of Riordan's present age. Leave your answer in its simplest form.

	Riordan	Riordan's son	Riordan's cousin	Difference between Riordan and Riordan's son
Before	10 u - 10	5 u - 10	2 u - 10	35
Change	+ 10	+ 10	+ 10
After	2x5	1x5
		5x1	2x1
Comparing Riordan, his son and his cousin in the end	10 u	5 u	2 u	5 u

The repeated identity is the age of Riordan's son. LCM of 1 and 5 is 5.

The difference in age between Riordan and Riordan's son remains unchanged.

Difference in age between Riordan and Riordan's son
= 10 u - 5 u 
= 5 u 

5 u = 35

1 u = 35 ÷ 5 = 7

His cousin's present age 
= 2 u - 10
= 2 x 7 - 10
= 14 - 10
= 4

Riordan's present age
= 10 u - 10
= 10 x 7 - 10
= 70 - 10
= 60

His cousin's present age as a fraction of Riordan's present age
= ⁴₆₀
= ¹₁₅

Answer(s): ¹₁₅