Question 904234
the slopes of the two lines will have -1 as their product
-9,-4,4,-1
slope 3/13
perpendicular slope -13/3
-3,6,4,k 
x-3-4=-7
6-k

(6-k)/-7=-13/3
3*(6-k)=13*7
18-3k=91
-3k=109
k=-109/3