The green box with the question mark in it is the slope of the line.
The slope is the change in Y over the change in X:
The change in Y = 0-22 = -22
The change in X = 3 - -8 = 3+8 = 11
The slope becomes : -22 / 11 = -2
The green box after the + sign is the y-intercept.
To find the Y-intercept use y = mx +b
b is the y intercept.
m is the slope.
Replace y and x with the coordinates of the first point and solve for b:
22 = -2(-8) + b
Simplify:
22 = 16 + b
b = 22-16
b = 6
The y-intercept = 6
The final equation becomes: y = -2x +6