In a room filled with 7 people, 4 people have exactly 1 sibling in the room and 3 people have exactly 2 siblings in the room. If two individuals are selected from the room at random, what is the probability that those two individuals are not siblings?
In a village of 100 households, 75 have at least one DVD player, 80 have at least one cell phone and 55 have at least one MP3 player. If.r and y are respectively the greatest and lower possible number of households that have all three of these devices, what is the value of x-y?