Let m denote the number of minutes.
Plan A:
The customer pays a monthly fee of $30 and then an additional 9 cents per minute of use.
Mathematically,
[tex]30+0.09m[/tex]
Plan B:
The customer pays a monthly fee of $33.60 and then an additional 8 cents per minute of use.
Mathematically,
[tex]33.60+0.08m[/tex]
For what amounts of monthly phone use will Plan A cost less than Plan B?
[tex]30+0.09m<33.60+0.08m[/tex]
Let us solve the above inequality for m
[tex]\begin{gathered} 30+0.09m<33.60+0.08m \\ 0.09m-0.08m<33.60-30 \\ 0.01m<3.60 \\ m<\frac{3.60}{0.01} \\ m<360 \end{gathered}[/tex]
This means that for less than 360 minutes, plan A will cost less than Plan B.
