Flux (in S.I. units) coming out and eantering a closed surface is shown in the figure. Find change enclosed by the closed surface.

Explanation

Net flux through the closed surface `= +20 + 30 + 10 - 15 = 45 N.m^(2)//c`
from Gauss's theorem
`phi_("net") = (q_("in"))/(epsilon_(0))`
`45 = (q_("in"))/(epsilon_(0)) rArr q_("in") = (45)epsilon_(0)`