Answer:
18
Step-by-step explanation:
You want to know the number of pencils in a box when 7 more than 4 boxes totals 79 pencils.
Let b represent the number of pencils in a box. Then the total number of pencils Mr. Ridley has is ...
4b +7 = 79
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.