Exercise 99 Page 471

Let's start by graphing $△GHJ.$

To determine the area of the triangle, we have to define its base and height. Notice that $\overline{JG}$ is a vertical segment. If we extend $\overline{JG}$ in the positive vertical direction, the height must be the horizontal distance between $H$ and the extended segment.

Now we can calculate the area of the triangle.