The slope-intercept form:
[tex]y=mx+b[/tex]
m - slope
b - y-intercept
The formula of a slope:
[tex]m=\dfrac{y_2-y_1}{x_2-x_1}[/tex]
substitute the coordinates of the points (8, 0) and (20, 12) to the formula:
[tex]m=\dfrac{12-0}{20-8}=\dfrac{12}{12}=1[/tex]
y = 1x + b = x + b
Put the coordinates of the point (8, 0) to the equation of a line:
0 = 8 + b subtract 8 from both sides
-8 = b