Answer
$x=\pm\sqrt{13}$
Work Step by Step
Substitute $10$ to $g(x)$ to obtain:
$10=\sqrt{x^2-4}+7\\
10-7=\sqrt{x^2-4}\\
3=\sqrt{x^2-4}$
Square both sides to obtain:
$3^2=\left(\sqrt{x^2-4}\right)^2\\
9=x^2-4\\
9+4=x^2\\
13=x^2$
Take the square root of both sides to obtain:
$\pm\sqrt{13}=x$
