They are using the point (2, 8) to write this equation. You know that because of the "y-8" in the equation, and also because it's bolded! lol. Anyways, what's missing is the slope and the x value from our point. The slope is -2. Find this by picking 2 points on the line and putting those into the slope equation. Use the bolded point and the x-intercept: (2,8) and (6,0):
. As stated earlier the x coordinate in the bolded point is 2. So our equation is y-8=-2(x-2). And there you Go!