Answer:
Undefined
Step-by-step explanation:
[tex]y=-7[/tex] has a slope of [tex]0[/tex], since it is a horizontal line. The only types of lines that are perpendicular to horizontal lines are vertical lines, which are usually in the form [tex]x=a[/tex] (where [tex]a[/tex] is any real number). Vertical lines have an undefined slope, so the answer is undefined. Hope this helps!