The equation for the first part would be 4.50p+40=112.
This is because he earns 40 dollars in wages which doesn't change but the number of shoes he commissions, which would be 4.50 per pair. varies based on how many he commissions.
The answer to your second part would be 16.
To find the number, you subtract 40 from each side which gets you 4.50 = 72. From there you just divide which gets you 16.
Another easy way to do it would just be substituting until you find the right number like on a calculator but if you don't have a calculator on hand (let's say for a test), than the first way would be more effective.
