Answer
$7.5$ gallons
Work Step by Step
The given table has the last column with values $\left[\begin{array}{l}
0.05x\\
0.10(5)=0.50\\
0.07(x+5)
\end{array}\right]$
The equation to solve is
$ 0.05x+0.5=0.07(x+5)\qquad$ ... multiply with 100
$5x+50=7(x+5)$
$ 5x+50=7x+35\qquad$ ... add $(-5x-35)$
$15=2x$
$x=\displaystyle \frac{15}{2}=7.5$ gallons
