On the right, there are 8 spheres. Since the scale is balanced, we can assume there is an equivalent of 8 spheres on the left side. We can clearly see three spheres (in red), so we'll subtract that from the 8. The canisters (blue) are the same weight, and make up 5 spheres togther. So, divide by 2, and your answer is the blue canister is equal to 2.5 spheres/counters.
