Carli and Angela share a cell phone plan and split the bill each month. Last month, their total bill was $109. Carli went over her data limit on her phone, so her share of the bill was $15 more than Angela's to account for the overage charge. Which system of equations represents this situation?

For this case, the first thing we must do is define variables.
 We have then:
 x = Carli's bill
 y = Angela's bill
 We have then:
 "their total bill was $ 109"
 x + y = 109
 "Carli went over her data limit on her phone, so her share of the bill was $ 15 more than Angela's"
 x = y + 15
 Answer:
 A system of equations that represents this situation is:
 x + y = 109
 x = y + 15