Exercise 24 Page 384

Let's start by drawing an arbitrary plane $\mathcal{C}.$

The intersection of two non-parallel planes is always a line. Therefore, we will draw another plane, $\mathcal{D},$ that is not parallel with and intersects $\mathcal{C}.$

Lastly, we will draw a line where the two planes intersect. Note here that the line is to be named $\overleftrightarrow{XY}.$ Thus, we have to place the two points $X$ and $Y$ on the line as well.