During the summer, a river's height decreases by 0.05 inch every day. What is the change in the river's height after 20 days?

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.