Anyone smart enough to do this?

What is the missing reason in step 5? linear pair postulategivendefinition of complementary anglescongruent complements theorem

Part a: sam rented a boat at $225 for 2 days. if he rents the same boat for 5 days, he has to pay a total rent of $480. write an equation in the standard form to represent the total rent (y) that sam has to pay for renting the boat for x days. (4 points)

Find the nonpermissible replacement for binthis expression. b2/5b +5