Supplementary angles are angles which add up to 180. To solve this, add the values of both angles and set it equal to 180, (4x-8)+(2x+2)=180. First, combine like terms, 6x-6=180. Now, solve for x, add 6 from both sides, 6x=186, divide by 6, x=186/6=31. This makes x equal to 31, making your answer A.