Question

A girl had 20 coins in nickels and dimes whose Sun was $1.40. She spent 65¢ using 8 coins. She has __ nickels.

Answer 1

5n+10(8-n) = 65
-5n = -15
n = 3

she spent 3 nickels and 5 dimes.

So, starting with N nickels and D dimes,

5N+10(20-N) = 140
-5N = -60
N=12

So, she is left with 9 nickels.