Will an object with weight of 90 N and a buoyant force of 85 N sink or float?
It will sink.
If those two forces are the only forces being exerted on the object, you can draw a free body diagram to list the forces being exerted on the object:
The buoyant force pulls the object upwards by 85 N, and the weight force pulls it downwards by 90 N. Because the weight force exerts a greater force than the buoyant force, the object will move downwards in the y-direction, in this case, it will sink.
Hope this helps!