A collection of nickels and dimes is worth $4.40. There are 53 coins in all. How many nickels are there?
12
18
35
41

A Nickel is worth 5 cents or 0.05.
A Dime is worth 10 cents or 0.10

n + d = 53
0.05n + 0.10d = 4.40

n = 53 - d
0.05(53 - d) + 0.10d = 4.40
2.65 - 0.05d + 0.10d = 4.40
0.05d = 4.40 - 2.65
0.05d = 1.75
d = 1.75 / 0.05
d = 35

n = 53 - d
n = 53 - 35
n = 18

There are 18 nickels and 35 dimes.

0.05n + 0.10d = 4.40
0.05(18) + 0.10(35) = 4.40
0.90 + 3.5 = 4.40
4.40 = 4.40