College trig and algebra

Question

Alicia is deciding between two different cell-phone companies. E-Mobile charges $70 per month plus a $70 setup fee. Dart charges a much larger $250 setup fee, but only charge $60 per month.

a) For how many months would Alicia need to keep the Dart phone before it cost her the same total amount as the E-Mobile phone?_  months

b) The following graph shows a linear function describing the cost of an E-Mobile phone as a function of time (in months). Add a line for Dart to the graph, and draw the point on this graph that represents your solution to part a.

Answer 1

Hi Kadidja,

Use x=number of months

a)

70x+70=60x+250 (equal cost of total amount after x months)

When you solve this, you get x=18.

Therefore, Alicia will have to keep the Dart phone for 18 months before it cost her the same total amount as the E-mobile phone.

b)

Could you upload the graph you are referring to please?