Final answer:
The costs of the two plans will be equal at 425 minutes of calls.
Step-by-step explanation:
To find the number of minutes of calls for which the costs of the two plans will be equal, we need to set up an equation and solve for the variable.
For the first plan, the cost is $26 + $0.07m, where m represents the number of minutes of calls. For the second plan, the cost is $9 + $0.11m.
Setting the two costs equal to each other and solving for m, we get:
$26 + $0.07m = $9 + $0.11m
Combining like terms, we get:
$0.04m = $17
Dividing both sides by $0.04, we get:
m = 425 minutes
Therefore, the costs of the two plans will be equal at 425 minutes of calls.