Answer:
y = 3/7 x
Step-by-step explanation:
first we have to replace the value of the following formula with 2 points
m = (y2 - y1) / (x2 - x1)
m = (6 - 3) / (14 - 7)
m = 3 / 7
Now we are going to replace with the other point, to make sure that the 3 points belong to the function
y = mx + b
9 = 3/7 * 21 + b
9 = 9 + b
9 - 9 = b
0 = b
as b gave us zero it is not necessary to write the sum
y = 3/7 x