Answer:
15 nickels
Explanation:
Choose variables: n = number of nickels, d = number of dimes.
There are two pieces of information given:
There are 45 coins, so n + d = 45.
The total value is $3.75 (let's use cents in order to avoid decimals), so
5n + 10d = 375
Solve the first equation for d by subtracting n from both sides.
d = 45 - d
Substitute this expression for d in the value equation:
5n + 10(45 - n) = 375 See? The only variable is now n!
Distribute the 10 (multiply).
5n + 450 - 10n = 375
450 - 5n = 375
-5n = -75
n = 15
There are 15 nickels.