X=4
We know this because of the given information that both angels are vertical angles indicating that they’re the same measurement so we can make our equation 12x+8=-5x+76 and first add 5x to both sides in order to cancel out -5x on the right side now from this we have 17x+8=76 and subtract 8 from both sides to cancel positive 8 in the left side and now 17x=68 divide both sides by 17 and get x=4