A dime = 0.10
A nickel = 0.05
N + D = 28 coins
Rewrite this as N = 28 -D
0.10D + 0.05N = 1.95
Replace N withe the rewritten equation above:
0.10D + 0.05(28-D) = 1.95
Use the Distributive Property:
0.10D + 1.4 - 0.05D = 1.94
Add the like terms:
0.05D + 1.4 = 1.95
Subtract 1.4 from both sides:
0.05D = 0.55
Divide both sides by 0.05
D = 0.55 / 0.05
D = 11
Nickels = 28 - 11 = 17
There are 11 dimes and 17 nickels.