Answer:
you use slope formula m=y2-y1/x2-x1
m=21-11/5-3=15.8
Explanation:
so the 3 points you have are (-1,-9) (3,11) (5,21)
so i'm going to choose (3,11) and (5,21) 3 is x1 11 is y1
5 is x2 11 is y2
m=y2-y1/x2-x1
m=21-11/5-3=15.8
good luck :)
hopefully, this helps
have a great day !!