Notice that the left side and front side of the figure have a common edge.
See solution.
Practice makes perfect
Looking at the given figure, we will explain how it illustrates that the given statement is true.
Statement
Planes P and Q intersect in line r.
From the figure, we can see that the left side and front side have a common edge which is line r.
Postulate 2.7 reads as follows.
If two planes intersect,
then their intersection is a line.
Therefore, Plane P and Plane Q intersect in line r, which means that the given statement is true.
