How many wheels will two tricycles have between them?
Each tricycle has three wheels, and there are two tricycles. So: 2 tricycles x 3 wheels = 6 wheels
When speaking about wheels on opposite sides of road vehicles then the answer is an "axle". The axle may contain drive shafts to transmit power from the engine to each of a pair of wheels. Similarly steam railway engines have axles between opposite wheels, but may also have "connecting rods" between wheels, which are on the same side, so that more wheels can be driven to provide greater traction.