Need Help w/ Central Air Conditioning

[eovnu87435ds]

So the hot summer is coming, and the problems are starting back up with the central air conditioning. We have a 4 bedroom 2 floor house. My room, the room across the hall, and the kitchen all get lots of A/C, the other bedroom, and all the other downstairs rooms get moderate A/C, and the Master Bedroom gets next to nothing, so in the summer, when the thermostat is set to 72, my bedroom is 60, the moderate rooms are around 72, and the master bedroom is at 80. So what ends up happening is to get the master bedroom down to 72, the moderate rooms go to 60ish, and mine to 50-55ish!

So does anybody out there who knows a thing or 2 about central air conditioning? I was thinking getting a dozen or so 6" PC fans, and installing them in the ducts, but IDK if that'll work. I just need to get this air thing balanced out.
Please help!