The number of five-cent coins in a bag was ¹₃ the number of ten-cent coins. Xavier took out 15 ten-cent coins and exchanged them for five-cent coins. Then he put the money back into the bag. The number of ten-cent coins became ³₈ the number of five-cent coins. How much money was there in the bag?

	Make u the same (1)x3 = (3)	5-cent (1)	10-cent (2)
Before	3 u	1 u	3 u
Change	+ 90	+ 30	- 15
After	24 p	8 p	3 p

Value of 10-cent coins to be exchanged to 5-cent coins
= 15 x 10
= 150

Number of 5-cent coins to be exchanged from the 10-cent coins
= 150 ÷ 5
= 30

(3) = (2)
24 p - 90 = 3 p + 15
24 p - 3 p = 15 + 90
21 p = 105

1 p = 105 ÷ 21 = 5

Number of 5-cent coins in the end
= 8 p
= 8 p x 5
= 40

Value of 5-cent coins in the end
= 40 x 5
= 200¢

Number of 10-cent coins in the end
= 3 p
= 3 x 5
= 15

Value of 10-cent coins in the end
= 15 x 10
= 150¢

Total value of coins
= 200 + 150
= 350¢

$1 = 100¢
350¢ = $3.50 

Answer(s): $3.50