80% of Zara's amount was $638 more than Jeremy's amount. When Zara spent 65% of her amount and Jeremy spent 20% of his amount, they had the same amount of amount left. Find the amount that Jeremy had at first.

	80% of Zara's amount	Zara's amount	Jeremy's amount
Before	64 u	80 u	35 u
Change		- 52 u (- 65%)	- 7 u (- 20%)
After		28 u	28 u

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

Percentage of Jeremy's amount left
= 100% - 20%
= 80%

35% = ³⁵₁₀₀ = ⁷₂₀
80% = ⁸⁰₁₀₀ = ⁴₅

The amounts of amount that Zara and Jeremy had left were the same.
Make the numerators the same.

⁷₂₀ of Zara's amount = ⁴₅ of Jeremy's amount
²⁸₈₀ of Zara's amount = ²⁸₃₅ of Jeremy's amount

Amount that Zara had = 80 u

80% of the amount that Zara had
= 80 u x 80%
= 80 u x ⁸⁰₁₀₀
= 64 u

Difference between 80% of Zara's amount and Jeremy's amount
= 64 u - 35 u 
= 29 u

29 u = 638
1 u = 638 ÷ 29 = 22

Amount that Jeremy had at first
= 35 u
= 35 x 22
= $770

Answer(s): $770