If you plot the points on a graph then you can clearly see where point D goes, (-2, 3). Then, you can find the side length, which is 4.5 units. Multiply that by 4 and you get 18 units.
If Manfred hiked 2/7 of a 588 mile trail, then to find how many miles he has hiked all we need to do is multiply the total miles (588) by what fraction of the miles he has traveled (2/7): 588 * 2/7 = 1176 / 7 = 168
