Can you plz me on these easy questions

If f(x)=3x+1 and f^-1=x-1/3, then f^-1(7)=

Solving algebraic equations 2m+3=11

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.