Answer:
I'm not sure if you need the value of x or the entire angle measure, so I'll give you both.
x = 19
The angle measure is 46 degrees
Explanation:
The sum of a quadrilateral's interior angles is 360 degrees. With that knowledge, we can subtract the angle measures we have from 360. To do that, we must first add 115 + 118 + 81, which equals 314. Now, we do 360 - 314, which gives us the measure of the unknown angle, which is 46 degrees.
Now, we must find x. We write the equation 2x + 8 = 46 since we know what the angle measure is now. Then, we subtract 8 from both sides, which leaves us with 2x=38. Finally, we need to divide 2 on both sides. If your math is correct, you should end up with x = 19. Hope this helps!