Write a proportion that can be used to determine the height of the lighthouse

Which equation represents the partial sum of the geometric series?

Ijust need to see how to do this. so you don’t have to answer all of them just a step by step explanation of one.

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.