Im having audio trouble for my Xbox 360 VGA HD/AV Cable?

hey guys, i just spent 40 $ on this freaking cable, because i wanted to hook up my 360 to my 28 inch monitor. I can see the picture when i plug it in the back of my monitor. but for the red and white audio jacks, a whole different story. i cant find were to put these jacks anywere on my monitor, i even tried to put the jacks in my pc tower as a desperation tactic. whats the deal? do i need to buy an adapter? HELP ME, THIS IS 40$ GOING TO WASTE!