Give the numbers of the lockers that were touch by exactly 5 students

Ineed if you could explain and give me the answer you! this needs done

How do i simply this expression (quadratic formula basis) on a ti-84 or normal calculator?

Ebuka's monthly rent is $750. if ebuka pays the rent late, his landlord charges 4% interest per week that the payment is late. write a function that gives the total cost r(t), in dollars, of ebuka's rent if he pays it t weeks late.