All three angles in a triangle must add up to 180 degrees. The picture already tells you that B is 63 degrees. This means A and C should both add up 117 degrees. If A is 2x+8 and B is x+7, then A+B is 3x+15. This means that 3x+15 is equal to 117 degrees.
3x + 15 = 117
3x = 117 - 15
3x = 102
x = 102/3
x = 34
Now that we know that x is 34, we plug it in. X + 7 becomes 34 + 7 degrees which is equal to 41 degrees.
