Question

Cx+5c=7c solve for x assume c doesn't equal 0

Answer 1

Because we've assumed $c \neq 0$, we can safely divide by $c$ (if $c$ could equal zero, we would have to account for the case in which doing so would be to divide by zero).  Hence, we have:

$\begin{aligned} x+5=7 \end{aligned}$

Subtracting $5$ from both sides gives $x = \boxed{2}$.