Given, surface tension of the liquid is $S$.
Work done in blowing a soap bubble. So as to increase its radius from $R_{1}=R$ to $R_{2}=3 R$ is given by
$W=S \cdot 8 \pi\left[R_{2}^{2}-R_{1}^{2}\right]$
where $S=$ surface tension
$W =S \cdot 8 \pi\left[(3 R)^{2}-(R)^{2}\right]$
$=S \cdot 8 \pi\left[9 R^{2}-R^{2}\right]$
$=S \cdot 8 \pi \cdot 8 R^{2}=64 \pi R^{2} S .$