Answer
$c=121$
Work Step by Step
The given equation is
$\Rightarrow \sqrt c+12=23$
Subtract $12$ from each side.
$\Rightarrow \sqrt c+12-12=23-12$
Simplify.
$\Rightarrow \sqrt c=11$
Square each side of the equation.
$\Rightarrow (\sqrt{c})^2=11^2$
Simplify.
$\Rightarrow c=121$
Check $c=121$.
$\Rightarrow \sqrt c+12=23$
$\Rightarrow \sqrt {121}+12=23$
$\Rightarrow \sqrt {11^2}+12=23$
$\Rightarrow 11+12=23$
$\Rightarrow 23=23$
True.
Hence, the solution is $c=121$.
