Question 712944
That small equation, x=8 is the line x=8 in which y is all Real Numbers.  This is a vertical line with no slope (because it is a vertical line).  Now, what kind of line is perpendicular to a vertical line?  What is the slope of such a line?  ZERO.  Slope of zero means horizontal line.  


You are looking for a horizontal line containing (-7,7).  Finish?





{{{highlight(y=7)}}}
Or if you want something that looks more interesting, 
{{{highlight(y=0*x+7)}}}