Chang has 36 coins, all dimes and half-dollars. The total value of all these coins is $12.00. How many dimes does he have?

6

21

15

18

The first thing we must do for this case is to define variables.

We have then:

x = number of dimes

y = number of half-dollars

We write the system of equations:

x + y = 36

0.10x + 0.50y = 12

Solving the system we have:

x = 15

y = 21

Answer:

He has 15 dimes