Gillian had $400 less than Jack. Jack spent 0.7 of his money and Gillian spent 0.2 of her money. In the end, Jack and Gillian had the same amount of money left. Find the amount of money Gillian had at first.

	Gillian	Jack	Difference
Before	15 u	40 u	25 u
Change	- 3 u	- 4 u
After	12 u	12 u

0.7 = ⁷₁₀

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

0.2 = ¹₅

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

The amount that Jack and Gillian each had in the end is the same. Make the numerators the same. LCM of 3 and 4 is 12.

³₁₀ of Jack's amount = ⁴₅ of Gillian's amount
¹²₄₀ of Jack's amount = ¹²₁₅ of Gillian's amount

Amount that Gillian had less than Jack
= 40 u - 15 u
= 25 u

25 u = 400

1 u = 400 ÷ 25 = 16

Amount that Gillian had at first
= 15 u
= 15 x 16
= $240

Answer(s): $240