Question

John has 18 coins worth $1.25. Some are nickels and dimes. How many of each does he have?

Answer 1

X nickels.
(18-X) dimes.

5x + 10(18-X) = 125 Cents.
5x + 180 - 10x = 125
5x = 180-125 = 55
X = 11

(18-X) = 18-11 = 7.