A supplementary angle can be two angles that sum up to 180 if you want you can have 2 angles that are 90 degrees that add up to 180 so therefore that would make a right angle.
3x + 24 = (3)(x) + (3)(8) You can see that there is multiplier 3 near x and 8. You can factor it and make 3x + 24 = 3(x + 8) So, the answer is 3. Hope this helps!
