Please solve this equation.

You got a job selling magazines door-to-door. you are paid $100 per day plus $1.50 for each magazine you sell. which recursive formula models this situation?

Aconstruction worker has rope 9 m long he needs to cut it in pieces that are each 3 /5 m long how many such pieces can he cut without having any rope leftover?

What is the axis of symmetry of the function f(x)=-(x+ 9)(x-21)