¹₂ of Justin's savings comprised of 20-cent coins and 10-cent coins. Justin used some 20-cent coins to purchase a game card. The number of 10-cent coins left was 40% more than the number of 20-cent coins left. Given that Justin had 30 more 10-cent coins than 20-cent coins left in the end, find the amount of money Justin spent on the game card.

	20-cent coins	10-cent coins
Before	1x7 = 7 u	1x7 = 7 u
Change	- 2 u
After	5x1 = 5 u	7x1 = 7 u

Fraction of Justin's savings that comprised of 10-cent coins
= 1 - ¹₂
= ¹₂

Number of 10-cents coins in the end in percentage
= 100% + 40%
= 140%

140% = ¹⁴⁰₁₀₀ = ⁷₅

Number of 10-cent coins remains unchanged. Make the number of 10-cent coins the same.  LCM of 1 and 7 is 7.

Number of more 10-cent coins than 20-cent coins
= 7 u - 5 u
= 2 u

2 u = 30

1 u = 30 ÷ 2 = 15

Number of 20-cent coins spent on the game card 
= 7 u - 5 u
= 2 u
= 2 x 15
= 30

Amount that Justin spent on the game card 
= 30 x 0.2
= $6

Answer(s): $6