A waiting room is 2/3 full when 36 people are seated. How many people are in the waiting room when it is 1/2 full?

When 36 people are seated the room is 2/3 full.

So for 1/3, 18 people are needed

It will be 3/3 full if 54 people are present

So there can be 54 people in total

Now for the room to be 1/2 full, people will be 1/2 x 54 = 27 people