I need help setting this equation up!!!!

Question

Every time Felicia does one of her chores, she gets 15 minutes to talk on the phone. When

she does not perform one of her chores, she gets 20 minutes of phone time taken away. This

week she has done her chores 5 times more than she has not performed her chores. In total,

she has accumulated 165 minutes of phone time. How many times has Felicia not performed her

chores?

Answer 1

Let a = the # of times she's done her chores and b = the # of times she hasn't.

a = 5b

15a - 20b = 165

Suuuubstitute.

15(5b) - 20b = 165

75b - 20b = 165

55b = 165

b = 3 times