80 nickels and dimes were dropped into a machine and got paid $7.15 for all of them. How many dimes were dropped into the machine?

Question

I need how many dimes AND nickels were dropped into the machine

Answer 1

n represents the number of nickels

80 - n represents the number of dimes

0.5n + 0.10(80 - n) = 7.15

Can you solve for n and answer?

Answer 2

N: Number of Nickles

D: Number of dimes

N+D=80

5N+10D=715 --> 5(N+D)+5D=715 --> 400+5D=715 --> D=315/5=63 -->N=17

check: 17*5+630=715