Answer
8 GB of data consumption is required for both plans to cost the same -- that is, $\$160$.
Work Step by Step
Let x be the number of GB of data per month that makes the charge the same.
The cost of the 2 data plans is to be the same. Therefore,
$20x=15x+40$
The above equation can be represented as below:
$\begin{align}
& 5x=40 \\
& x=8
\end{align}$
And, the value of each plan is given below:
$\begin{align}
& 20x=20\times 8 \\
& =160
\end{align}$
Or,
$\begin{align}
& 15\times x+40=15\times 8+40 \\
& =160
\end{align}$
Hence, the number of GB for which the cost of both plans is the same is 8 GB. The cost of each plan is $160.
