Answer
$q=-4.3nC$
Work Step by Step
We know that:
$\phi_{total}=(-34)\times (3\times 3)+20(-3\times 3)=-486\frac{N.m^2}{C}$
According to Gauss's law;
$\phi_{total}=\frac{q}{\epsilon_{\circ}}$
$\implies q=\epsilon_{\circ}\phi_{total}$
We plug in the known values to obtain:
$q=(8.85\times 10^{-12})(-486)=-4.3\times 10^{-9}=-4.3nC$
