2. Let the number of teeth of B be y, then: 9y=2x, and substitute x=8 1 to get y= 18.

Let A turn to 8 turn to B turn to Z turn: 45*8= 18z and z=20.

3.b rotates counterclockwise and c rotates clockwise, which can be seen by demonstrating it with your hands. If we must say the principle, we can explain it from the force direction of gear meshing.