Answer:
4.05 pounds
Explanation:
You want to know the weight that can be added to 2.65 pounds and 10.8 pounds if the total is to be 17.5 pounds.
Additional weight
The available capacity is the difference between the capacity and the weight already in the container:
17.5 lb -2.65 lb -10.8 lb = 4.05 lb
The container can hold up to 4.05 more pounds.