Answer
greater than $200$ calls
Work Step by Step
Let $x$ be the number of calls per month.
Plan 1 is more economical than Plan 2 if Plan 2 is greater than Plan 1. That is,
\begin{array}{l}\require{cancel}
13+0.06x\gt25
.\end{array}
Using the properties of inequality, then
\begin{array}{l}\require{cancel}
0.06x\gt25-13
\\\\
0.06x\gt12
\\\\
x\gt\dfrac{12}{0.06}
\\\\
x\gt200
.\end{array}
Hence, if there are $\text{
greater than $200$ calls
,}$ Plan 1 is more economical than Plan 2.