Aballoon that weighs 1 n is suspended in air, drifting neither up nor down. (a) how much buoyant force acts on it? (b) what happens if the buoyant force decreases? (c) if the buoyant force increases?

(a) If the balloon is suspended in air and it drifts neither up nor down, it means the forces acting on it are equally balanced. There are only two forces acting on the balloon: 
- its weight, of magnitude 1 N, directed downward
- the buoyant force, directed upward
The two forces are balanced, so the buoyant force in this case is equal to the weight of the balloon: 1 N.

(b) when the buoyant force decreases, the weight becomes greater than the buoyant force. This means there is now a net force on the balloon, acting downward, so the balloon starts to drift toward the ground.

(c) when the buoyant force increases, it becomes greater than the weight. This means there is now a net force on the balloon, acting upward, so the balloon starts to go up.

Does this your question?