Slope is defined as the change in y divided by the change in x. We note that for x=0, the value of y is 8.000 and for x=2.000, the value of y is 4.000. So, for a change of 2.000 in x (The change in x is sometimes referred to as "RUN") we get a change of 4.000 - 8.000 = -4.000 in y. (The change in y is sometimes referred to as "RISE" and the Slope is m = RISE / RUN)
The straight lines equal 180 and you subtract 180 to 150 and 180 to 100 to get 30 and 80 and the inside of a triangle is 180 and you subtract 30 and 80 to 180 to get 70.
