The error is 8(x - 3) + 7 = 2x(13) and -17 = 34x.
4 - 17 = -13, not 13
8x - 17 = 26x
-17 = 26x -8
-17 = 18x ( it should be like this, but this is still wrong because it should -26)
The solution is:
8(x - 3) + 7 = 2x(4 - 17)
8(x - 3) + 7 = 2x(-13)
8x - 24 + 7 = -26x
8x - 17 = -26x
8x + 26x = 17
34x = 17
x = 17/34
x = 1/2
Hope it helps!