Question 499472
substitute -7 for z into the expression.  Put parenthesis around it so you don't get confused.
I think that you may have your expression written wrong, so I am hesitant to solve this for you.
{{{2z-1/z-8}}}will equal  is different than {{{(2z-1)/(z-8)}}}
the second equation will be equal to 1, the first equation will be a fraction