Answer
More than $200$ minutes of calls
Work Step by Step
Let the number of minutes of calls in a month be $x$.
Plan A charges $\$25$ per month for unlimited calls.
Plan B charges $\$13$ per month plus $\$0.06$ per minute.
In the mathematical form.
Plan A charges for a month $=25$.
Plan B charges for a month $=13+0.06x$.
For the plan A to be better deal the inequality is.
Plan B charges $>$ plan A charges.
The inequality is
$\Rightarrow 13+0.06x>25$.
Subtract $13$ from both sides.
$\Rightarrow 13+0.06x-13>25-13$.
Simplify.
$\Rightarrow 0.06x>12$.
Divide both sides by $0.06$.
$\Rightarrow \frac{0.06x}{0.06}>\frac{12}{0.06}$.
Simplify.
$\Rightarrow x>200$.
Hence, more than $200$ minutes of calls in a month make plan A the better deal.
