Exercise 33 Page 385

To begin with, we have to figure out where the two planes are located in the diagram. The points $A,$ $E,$ and $H$ are all on the front face of the cube, so when we extend the front face in all directions, we get plane $AEH.$ Similarly, plane $FBE$ is the left face of the cube extended in all directions.

These planes intersect at the left border of the front face. This occurs along the line $\overleftrightarrow{AE}.$