Joey decides to empty his piggy bank and count his money. His bank is filled with only nickels and dimes. Joey counted a total of 45 coins that added up to $3.15. How many nickels and how many dimes does Joey have in his piggy bank?

Joey has 18 nickles and 27 dimes in his piggy bank.

Step-by-step explanation:

1 nickle = 5 cents

1 dime = 10 cents

$1 = 100 cents

$3.15 = 135 cents

Let

n represent the number of nickles, n>=0

d represent the number of dimes, d>=0

Joey counted a total of 45 coins that added up to $3.15:

n + d = 45

5n + 10d = 315

n = 18 nickles

d = 27 dimes