Question 23669
First of all, a line with undefined slope is a VERTICAL LINE.  Any line that is perpendicular to a VERTICAL LINE is a HORIZONTAL LINE.  A vertical line is a line in the form x= some number.  A horizontal line is a line in the form y = some number.  In this case a HORIZONTAL LINE that passes through (7,9) will be a line in the form of y = some number, and that number would be 9.  


That's my final answer:  y = 9.


R^2 at SCC