Step-by-step explanation:
Collinear points have the same gradient
find the gradient(slope) between AB first

Find the one for BC

Find the gradient between AC now

YOUR LAST STATEMENT NOW WILL BE
POINTS A,B AND C ARE COLLINEAR SINCE THE GRADIENTS BETWEEN THEM IS THE SAME!!!
You have to calculate how many ways you can select six things (r)
from a set of 9 things (n). (See attached formula).
9! / 6! * (3!) =
9*8*7 * 6! / 6! * 3! =
9*8*7 / 3! =
3 * 4 * 7 = 84 lineups
It seems that you have missed the necessary question for us to answer this problem. Anyway, please complete it first and I will try to get back to you and try to help. Let me know. Have a great day ahead!