1 pack of orbit gum weighs .079 pounds (as per amazon).
2 packs weigh .158 pounds.
The case plus DVD weighs .188 pounds (as per Jeff).
The weight of 2 packs of gum + DVD equals .346
John is carrying 49.824 lbs of GUM
Sally is carrying 110.72 lbs of GUM (to get the above 2 numbers, multiply the weight of the DVD + 2 packs of gum times the amount they have).
To make it fair, each of them would have to weigh 150 pounds, meaning that John would have to be left with 14 pounds of GUM and Sally would have to be left with 29 pounds of GUM (what a waste of perfectly good GUM

).
To find out the weight of GUM needed to throw out, subtract the amount they are able to carry from the total amount of GUM they have.
The amount of GUM that John would throw out would be equal to 35.824 lbs. It can be found with the following equation: 35.824 = .346X , with X being the number of GUM packages needed to be thrown out. X = 103.54, which gets rounded up to 104. John would have to throw out 104 cases of the GUM + 2 orbitz gums packages.
The amount of GUM that Sally would throw out would be equal to 81.72 lbs. It can be found with the following equation: 81.72 = .346X , with X being the number of GUM packages needed to be thrown out. X = 236.185, which gets rounded up to 287. Sally would have to throw out 287 cases of the GUM + 2 orbitz gums packages.
Sally would have to throw out 183 more than John would.
EDIT: I just posted this in the holiday promo thread and saw there was a thread devoted to the contest, so am copying and pasting my answer.