⁷₁₀ of Henry's savings comprised of 20-cent coins and 50-cent coins. Henry used some 20-cent coins to purchase a glowstick. The number of 50-cent coins left was 25% more than the number of 20-cent coins left. Given that Henry had 15 more 50-cent coins than 20-cent coins left in the end, find the amount of money Henry spent on the glowstick.

	20-cent coins	50-cent coins
Before	7x5 = 35 u	3x5 = 15 u
Change	- 23 u
After	4x3 = 12 u	5x3 = 15 u

Fraction of Henry's savings that comprised of 50-cent coins
= 1 - ⁷₁₀
= ³₁₀

Number of 50-cents coins in the end in percentage
= 100% + 25%
= 125%

125% = ¹²⁵₁₀₀ = ⁵₄

Number of 50-cent coins remains unchanged. Make the number of 50-cent coins the same.  LCM of 3 and 5 is 15.

Number of more 50-cent coins than 20-cent coins
= 15 u - 12 u
= 3 u

3 u = 15

1 u = 15 ÷ 3 = 5

Number of 20-cent coins spent on the glowstick 
= 35 u - 12 u
= 23 u
= 23 x 5
= 115

Amount that Henry spent on the glowstick 
= 115 x 0.2
= $23

Answer(s): $23