Find the value of $x$ such that $\sqrt{x - 4} = 4$.
To solve for $x$, I need to get rid of the square root on the left side. I can do that by squaring both sides of the equation, since $(\sqrt{a})^2 = a$ for any positive $a$. Squaring both sides gives me $x - 4 = 16$. Now I just need to add $4$ to both sides to isolate $x$. Doing that, I get $x = 20$. To check my answer, I can plug it back into the original equation and see if it makes it true. I get $\sqrt{20 - 4} = \sqrt{16} = 4$, which is correct. Therefore, $x = 20$ is the solution. 