[tex]17 = \frac{(2x + 4) + (8x - 50)}{2}= \frac{10x - 46}{2} [/tex]
so
[tex]17 \times 2 = 10x - 46[/tex]
[tex]34 + 46 = 10x[/tex]
[tex] \frac{80}{10} = x[/tex]
[tex]8 = x[/tex]