Answer
$120$ mL
Work Step by Step
The given table has the last column with values $\left[\begin{array}{l}
0.05x\\
0.20(60)=12\\
0.10(x+60)
\end{array}\right]$
The equation to solve is
$ 0.05x+12=0.10(x+60)\qquad$ ... multiply with 100
$5x+1200=10(x+60)$
$ 5x+1200=10x+600\qquad$ ... add $(-5x-600)$
$600=5x$
$x=\displaystyle \frac{600}{5}=120$ mL
