Answer
The number of messages, such that, the cost for the plan A is same as plan B are 200.
Work Step by Step
The total charges per month for plan A with unlimited texting is \[\$25\]and this is same as the cost of plan B. Let the number of messages be denoted by m, then, the charges with respect to the usage of messages for plan B, that is \[\$13\], such that the cost for both the plans is same, can algebraically be stated as,
\[\begin{align}
& 13+0.06m=25 \\
& 0.06m=25-13 \\
& m=\frac{12}{0.06} \\
& m=200
\end{align}\]
The number of messages, such that, the cost for the plan A is same as plan B are 200.
