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 ?

One line.

Step-by-step explanation:

We know that a plane is a two dimensional flat platform , which has infinite length and width.It contains infinite number of lines.

The intersection of two planes is a line .

Given statement : Brenda observes that the keyboard and the screen of an open laptop lie on two different planes.

Then In only one line the planes containing the keyboard and the screen intersect .

step-by-step explanation:

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i belive those are the ones that are under 90 degreese.