As m is parallel to n, the angles (8x-7) and (x+16) are supplementary (they add 180 degrees).
Then, we can write:
[tex]\begin{gathered} (8x-7)+(x+16)=180 \\ 8x+x-7+16=180 \\ 9x+9=180 \\ 9x=180-9 \\ 9x=171 \\ x=\frac{171}{9} \\ x=19 \end{gathered}[/tex]The value of x is 19.