⁵₈ of Tom's savings comprised of 20-cent coins and 50-cent coins. Tom used some 20-cent coins to purchase a glowstick. The number of 50-cent coins left was 40% more than the number of 20-cent coins left. Given that Tom had 90 more 50-cent coins than 20-cent coins left in the end, find the amount of money Tom spent on the glowstick.

	20-cent coins	50-cent coins
Before	5x7 = 35 u	3x7 = 21 u
Change	- 20 u
After	5x3 = 15 u	7x3 = 21 u

Fraction of Tom's savings that comprised of 50-cent coins
= 1 - ⁵₈
= ³₈

Number of 50-cents coins in the end in percentage
= 100% + 40%
= 140%

140% = ¹⁴⁰₁₀₀ = ⁷₅

Number of 50-cent coins remains unchanged. Make the number of 50-cent coins the same.  LCM of 3 and 7 is 21.

Number of more 50-cent coins than 20-cent coins
= 21 u - 15 u
= 6 u

6 u = 90

1 u = 90 ÷ 6 = 15

Number of 20-cent coins spent on the glowstick 
= 35 u - 15 u
= 20 u
= 20 x 15
= 300

Amount that Tom spent on the glowstick 
= 300 x 0.2
= $60

Answer(s): $60