Answer
$C_2=C_T-C_1-C_3-C_4$
Work Step by Step
To solve the given equation for $ C_2$, we keep $ C_2$ and move out all other terms to the other side as follows:
$$
C_T=C_1+C_2+C_3+C_4\Longrightarrow C_T-C_1-C_3-C_4=C_2\\\
\Longrightarrow C_2=C_T-C_1-C_3-C_4
.$$
