#### Answer

0

#### Work Step by Step

The line $y-7=0$ also can be written as $y=7$.
$y=7=0x+7$ is written in the form $y=mx+b$, where m is the slope of the line.
$m=0$, so the slope of the line is zero. In general, horizontal lines, which are written in the form $y=b$, have a slope of zero.