Question

A closed surface which encloses a charge has an electric flux of 15.8 N.m^2/C. What is the magnitude of the charge?

Answer 1

The electric flux through surface

$$\Phi=\oint EdA=\frac{q}{\epsilon_0}$$

Hence, the net charge

$$q=\Phi \epsilon_0\\ =15.8*8.85*10^{-12}=1.4*10^{-10}\:\rm C$$