We can write the cost function for UPS and FedEx depending on p (pounds).
UPS charges $7 for the first pound, and $0.20 for each additional pound. That means that there is a fixed cost and then a variable cost for every pound exceeding the first pound.
We can write this as:
The same happens for FedEx, but with different fixed and variable cost for the extra pounds:
We can calculate how many pounds will it take for both to cost the same by making both cost equal and solving for p:
At p=21 pounds, both services cost the same.