First we must solve for x:
[tex]\begin{gathered} 2(x+4)-3x=17 \\ \Rightarrow2x+8-3x=17 \\ \Rightarrow-x=17-8=9 \\ \Rightarrow x=-9 \end{gathered}[/tex]Now, since x=-9, we just have to find the value of x-7:
[tex]\begin{gathered} x=-9 \\ \Rightarrow x-7=-9-7=-16 \end{gathered}[/tex]Therefore, x-7=-16
