PLEASE HELP THIS IS ALG 2 I NEED HELP

Given a: b and b: c, find a: b: c. write the ratio in simplest form. a: b=6: 10 and b: c=21: 33

Twelve less than a number is at most 20

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.