If $7 - 4x = 15$, what is the value of $8x + 2$?
I can do this by subtracting $7$ from both sides, which gives me $-4x = 8$. Then, I can divide both sides by $-4$ to get $x = -2$. Now that I know $x = -2$, I can substitute it into the expression $8x + 2$. This gives me $8(-2) + 2 = -16 + 2 = -14$. 