Set up the equation for both plans:
[tex]\text{First plan: } 24 + 0.15x[/tex]
24 is the monthly fee. 0.15 is the cost per minute of calls. x is the amount of minutes of calls.
[tex]\text{Second plan: } 0.19x[/tex]
There is no monthly fee. 0.19 is the cost per minute of calls, and x is the amount of minutes of calls.
Because the question asks for the amount of minutes where the plans will cost the same, the equations will equal each other:
[tex]24 + 0.15x = 0.19x[/tex]
Subtract 0.15x from both sides:
[tex]24 = 0.04x[/tex]
Divide both sides by 0.04 to get x by itself:
[tex]x = 600[/tex]
The cost of the two plans will be equal at 600 minutes of calls.
