Identify the slope, m. This can be done by calculating the slope between two known points of the line using the slope formula.
Find the y-intercept. This can be done by substituting the slope and the coordinates of a point (x, y) on the line in the slope-intercept formula and then solve for b.
First, realize that angle ABC is the sum of the two other angles. Hence, form an equation in which you subtract the measure of one of the angles from angle ABC to get the measure of the other angle -- the one you are solving for.
