Answer
$v=5$.
Work Step by Step
The given equation is
$\Rightarrow 5=10-v$
Add $v-5$ to both sides.
$\Rightarrow 5+v-5=10-v+v-5$
Simplify.
$\Rightarrow v=5$
Check:-
$\Rightarrow 5=10-5$
$\Rightarrow 5=5$
True.
Hence, the solution is $v=5$.