If you would like to know how much will 2 1/2 bags of trail mix weigh, you can calculate this using the following steps:
1 bag ... 1 1/3 pounds = 4/3 pounds
2 1/2 bags = 5/2 bags ... x pounds = ?
1 * x = 4/3 * 5/2
x = 4/3 * 5/2 = 10/3 = 3 1/3 pounds
Result: 2 1/2 bags of trail mix will weigh 3 1/3 pounds.