If $7 - 4x = 15$, what is the value of $8x + 2$?
Subtracting 7 from both sides of the first equation gives $-4x=8$. Dividing both sides of this by $-4$ gives $x=-2$. Now that we know what $x$ is, we can substitute it into $8x+2$ to get $8(-2)+2=-16+2=\boxed{-14}$.