80% of Diana's amount was $572 more than Oliver's amount. When Diana spent 55% of her amount and Oliver spent 30% of his amount, they had the same amount of amount left. Find the amount that Oliver had at first.

	80% of Diana's amount	Diana's amount	Oliver's amount
Before	112 u	140 u	90 u
Change		- 77 u (- 55%)	- 27 u (- 30%)
After		63 u	63 u

Percentage of Diana's amount left
= 100% - 55%
= 45%

Percentage of Oliver's amount left
= 100% - 30%
= 70%

45% = ⁴⁵₁₀₀ = ⁹₂₀
70% = ⁷⁰₁₀₀ = ⁷₁₀

The amounts of amount that Diana and Oliver had left were the same.
Make the numerators the same.

⁹₂₀ of Diana's amount = ⁷₁₀ of Oliver's amount
⁶³₁₄₀ of Diana's amount = ⁶³₉₀ of Oliver's amount

Amount that Diana had = 140 u

80% of the amount that Diana had
= 140 u x 80%
= 140 u x ⁸⁰₁₀₀
= 112 u

Difference between 80% of Diana's amount and Oliver's amount
= 112 u - 90 u 
= 22 u

22 u = 572
1 u = 572 ÷ 22 = 26

Amount that Oliver had at first
= 90 u
= 90 x 26
= $2340

Answer(s): $2340