Explanation:
n= nickels
q= quarters
Create a system of equations
n + q =72 number of coins
0.05n + 0.25q = 12 amount in money
solve by elimination ( anything would be fine)
n + q = 72
4( 0.05n + 0.25q = 12)
n+ q = 72
-
0.2n + q = 48
0.8n = 24
n= 30
now use substitution to find how many quarters she has
30 + q = 72
q = 42
He has 30 nickels and 42 quarters
Sorry for skipping some steps
I hope this helps!!!