Question

Brenda observes that the keyboard and the screen of an open laptop lie on two different planes. In how many lines do the planes containing the keyboard and the screen intersect

Answer 1

The wording seems a bit odd to me, but I would think that the question is refering to the intersection between the two planes. If that is the case, I think there would be one definable line extending along the intersection.
An analogy would be to take a piece of paper, fold it in half, and then set it so the two halves form a right angle. There are now two planes with the crease of the paper being the line of intersection.
But again, the wording seems odd so I could be wrong.

Answer 2

Thank you so much for your help.