Let:
• y, be the cost of the plan
,• x, be the minutes spend on call
This way, we'll have:
Plan A:
[tex]y=0.12x+20[/tex]Plan B:
[tex]y=0.17x+13[/tex]If the two plans cost the same, we'll have that:
[tex]0.12x+20=0.17x+13[/tex]Solving for x :
[tex]\begin{gathered} 20-13=0.17x-0.12x \\ \rightarrow7=0.05x \\ \rightarrow\frac{7}{0.05}=x \\ \\ \Rightarrow x=140 \end{gathered}[/tex]A) The two plans will cost the same for 140 minutes on call
The cost will be:
[tex]\begin{gathered} y=0.12(140)+20 \\ \Rightarrow y=36.8 \end{gathered}[/tex]B) $36.80
