well, start with 7/3 because we're splitting the 7 pounds 3 differnt ways. this gives us a decimal of 2.3333 (the three is repeating). now just multiply the 2.33333 times 2 since it is going in two bags and you get about 4.67.
Another way to do this is to divide 7 by 2/3 since you are looking for how much is in 2 of the three bags, in which case the answer would still come out as 4.67.