Question

A horizontal line through point -7,8

Answer 1

We don't know what you want because you didn't ask any question. Would you like to know the equation of such a line ? Well, every point on a horizontal line has the same 'y' coordinate. The point you mentioned has the 'y' coordinate of 8, so it's on the horizontal line (here comes the answer) . . . Y = 8 .

Answer 2

$A\ horizontal\ line\ throught\ point\ (a;\ b):y=b\\\\therefore:\\\\point(-7;\ 8)\Rightarrow\boxed{y=8}$