Find the value of $x$ such that $\sqrt{1 - 3x} = 7$.
To solve for $x$, I need to isolate it on one side of the equation. I can start by squaring both sides to get rid of the square root on the left. Squaring both sides gives me $1 - 3x = 49$. Now I can subtract 1 from both sides to get $-3x = 48$. Then I can divide both sides by -3 to get $x = -16$. 