You are comparing the costs of producing shoes at two different manufacturers. Company 1 charges $5

You are comparing the costs of producing shoes at two different manufacturers. Company 1 charges $5 per pair of shoes plus a $650 flat fee. Company 2 charges $4 per pair of shoes plus a $700 flat fee. How many pairs of shoes are produced when the total costs for both companies are equal?

Let s be the number of shoes. We have two equations:
(1) C = 5s + 650
(2) C = 4s + 700

Set the costs equal to each other
5s + 650 = 4s + 700

Subtract 4s from each side
s + 650 = 700

Subtract 650 from each side
s =50