If you have 5 packages of brushes and 32 single brushes and each package has the same number of brushes. In all, he has 123 brushes for his students to use. How many brushes are in each packag?

We would start with this:

123-32 = 91 because of the amount of single brushes

Then we have 91 non-single brushes that are in the packages, and if there are 5 packages, then next we must divide.

91:5 ≈18 packages with 32 single brushes

5x+32=123

5x=91

x = 91/5 brushes