90% of Xylia's amount was $3128 more than Oscar's amount. When Xylia spent 65% of her amount and Oscar spent 10% of his amount, they had the same amount of amount left. Find the amount that Oscar had at first.

	90% of Xylia's amount	Xylia's amount	Oscar's amount
Before	162 u	180 u	70 u
Change		- 117 u (- 65%)	- 7 u (- 10%)
After		63 u	63 u

Percentage of Xylia's amount left
= 100% - 65%
= 35%

Percentage of Oscar's amount left
= 100% - 10%
= 90%

35% = ³⁵₁₀₀ = ⁷₂₀
90% = ⁹⁰₁₀₀ = ⁹₁₀

The amounts of amount that Xylia and Oscar had left were the same.
Make the numerators the same.

⁷₂₀ of Xylia's amount = ⁹₁₀ of Oscar's amount
⁶³₁₈₀ of Xylia's amount = ⁶³₇₀ of Oscar's amount

Amount that Xylia had = 180 u

90% of the amount that Xylia had
= 180 u x 90%
= 180 u x ⁹⁰₁₀₀
= 162 u

Difference between 90% of Xylia's amount and Oscar's amount
= 162 u - 70 u 
= 92 u

92 u = 3128
1 u = 3128 ÷ 92 = 34

Amount that Oscar had at first
= 70 u
= 70 x 34
= $2380

Answer(s): $2380