Question

Mr. Ridley has 4 boxes of pencils and 7 single pencils. In all, he has 79 pencils. How many

pencils are there in a box?

Answer 1

18

Explanation:

You want to know the number of pencils in a box when 7 more than 4 boxes totals 79 pencils.

Setup

Let b represent the number of pencils in a box. Then the total number of pencils Mr. Ridley has is ...

4b +7 = 79

Solution

This 2-step linear equation is solved in the usual way:

Step 1: isolate the variable term

4b +7 -7 = 79 -7 . . . . . . add the opposite of the left-side constant

4b = 72 . . . . . . . . . simplify

Step 2: isolate the variable

4b/4 = 72/4 . . . . . . . . . . divide by the coefficient of the variable

b = 18 . . . . . . . . . . simplify

There were 18 pencils in each of Mr. Ridley's pencil boxes.