To find slope use y2 - y1 / x2 - x1. I would suggest doing this twice just to make sure.
For this one, I will use the first three points. (2,2) (4,5) (6,8)
8 - 5 / 6 - 4 = 3/2
5 - 2 / 4 - 2 = 3/2 = your slope
Now, since there is no (0,y) given, we need to find the y-intercept using . . . You guessed it! Point - slope form! I will use the point (2,2)
y-y₁=m(x-x₁)
y - 2 = 3/2 (x - 2)
y - 2 = 3/2x -3
+2 +2
Y = 3/2x -1
-1 = your y-intercept form.