Answer:
r = 11/2
Step-by-step explanation:
m = slope
slope, m = (y2 - y1)/(x2 - x1)
-4 = (7 - 9)/(r - 5)
cross multiply
-4(r - 5) = 7 - 9
clearing brackets
-4r + 20 = -2
-4r = -22
r = 22/4 = 11/2
