13.44 is 22% of what number

What is the missing step in this proof ?

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.

Two numbers have a sum of -19. one number is x. what expression represents the other number?