equation given
[tex]\frac{6}{7}\x-8=7[/tex]
calculations
add 8 to both sides [tex]\frac{6}{7}x-8+8=7+8[/tex]
divide both sides by 6/7...
which means multiply by 7/6 [tex]\frac{6}{7}x\times\frac{7}{6}=15\times\frac{7}{6}[/tex]
So now you have [tex]x=15\times\frac{7}{6}=\frac{15\times7}{6}=\frac{105}{6}=17.5[/tex]
(Excuse me, I'm not used to the wonky LaTeX on this site...)