Pls help with explanation its 2 questions

Solve of x.

x/3 + 14 = 35

and

Solve of x.

-9x - 13 = -103

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.