Marion had $450 less than Bobby. Bobby spent 0.8 of his money and Marion spent 0.3 of her money. In the end, Bobby and Marion had the same amount of money left. Find the amount of money Marion had at first.

	Marion	Bobby	Difference
Before	10 u	35 u	25 u
Change	- 1 u	- 7 u
After	7 u	7 u

0.8 = ⁴₅

Fraction of Bobby's amount left
= 1 - ⁴₅
= ¹₅

0.3 = ³₁₀

Fraction of Marion's amount left
= 1 - ³₁₀
= ⁷₁₀

The amount that Bobby and Marion each had in the end is the same. Make the numerators the same. LCM of 1 and 7 is 7.

¹₅ of Bobby's amount = ⁷₁₀ of Marion's amount
⁷₃₅ of Bobby's amount = ⁷₁₀ of Marion's amount

Amount that Marion had less than Bobby
= 35 u - 10 u
= 25 u

25 u = 450

1 u = 450 ÷ 25 = 18

Amount that Marion had at first
= 10 u
= 10 x 18
= $180

Answer(s): $180