Question

Remi has $8.40 in a jar that contains only nickels and dimes. There are 108 coins in the jar. How many nickels are in the jar?
A. 22
B. 48
C. 55
D. 60

Answer 1

this is generally considered as a system of equation:

n + d = 108
5n + 10d = 840

solve for n

Answer 2

If you like reasoning it out, figure out how much you would have if you had only nickels. Compare that amount with the amount you want, and trade some of those nickels for dimes. The total will increase by 5 cents for each coin exchanged.