Separate LEGO Technic wheel from 3 pin hub
The main trick is to simultaneously push all three pins of the hub:


If you have another hub, and the wheel allows for this, take it and push carefully from the other side. If both hubs are half-way in, you should be able to pull out both.
Otherwise, take two wedge belt wheels, align them on top of each other, insert a pin into every second hole and repeat the above. There are various obvious variations of this approach using different parts, if you need a longer tool or don’t have the parts available.