3.1x+2.8z 4.3x-1.2z Subtract the following polynomials

Janie has $3. she earns $1.20 for each chore she does and can do fractions of chores. she wants to earn enough money to buy a cd for $13.50. write an inequality to determine the number of chores, c, janie could do to have enough money to buy the cd.

Ithink i know it but i want to be sure so can you me out ?

Need plz been trying to do it for a long time and still haven’t succeeded