Riordan's and Shannon's monthly allowances were the same at first. Riordan's allowance increased by 20% while Shannon's decreased by 10%. Given that Riordan's allowance would increase by another 25% if he had received $666 more from his Mothers, find the difference in the children's monthly allowances.

	Riordan	Shannon
Before	1 u	1 u
Change 1	+ 0.2 u	- 0.1 u
After 1	1.2 u	0.9 u
Change 2	+ 0.3 u	No change
After 2	1.5 u	0.9 u

Increase in Riordan's allowance
= 20% x 1 u
= ²⁰₁₀₀ x 1 u
= 0.2 u

Decrease in Shannon's allowance
= 10% x 1 u
= ¹⁰₁₀₀ x 1 u
= 0.1 u

Increase in Riordan's allowance if his Mothers gave another $666
= 25% x 1.2 u
= ²⁵₁₀₀ x 1.2 u
= 0.3 u

0.3 u = 666

1 u = 666 ÷ 0.3 = 2220

Difference in the allowance between Riordan and Shannon
= 1.2 u - 0.9 u
= 0.3 u
= 0.3 x 2220
= $666

Answer(s): $666