Tiffany had $425 less than Andy. Andy spent 0.8 of his money and Tiffany spent 0.3 of her money. In the end, Andy and Tiffany had the same amount of money left. Find the amount of money Tiffany had at first.

	Tiffany	Andy	Difference
Before	10 u	35 u	25 u
Change	- 1 u	- 7 u
After	7 u	7 u

0.8 = ⁴₅

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

0.3 = ³₁₀

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

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

¹₅ of Andy's amount = ⁷₁₀ of Tiffany's amount
⁷₃₅ of Andy's amount = ⁷₁₀ of Tiffany's amount

Amount that Tiffany had less than Andy
= 35 u - 10 u
= 25 u

25 u = 425

1 u = 425 ÷ 25 = 17

Amount that Tiffany had at first
= 10 u
= 10 x 17
= $170

Answer(s): $170