1) Gathering the data
1 jar
16p, 28dimes and 17 quarters + n = 81
2) Let's find how many nickels we have in this jar
16 +28 +17 +n =81
61+n=81 subtract 61 from both sides
n =20
Answering those questions we can state:
There are 61 coins that are not nickels
There are 20 coins that are nickels
16 +28 +17 +n =81