create a gear train or belt system with a mechanical advantage of 300. The gear sizes: 84, 60, 36, (teeth) Sprocket size: 30, 24, 18, 12, 6 (teeth)

Answer 1

In order to get a total gear ratio of 300, I would use 5*6*10, by selecting 60/12 * 36/6 * 60/6. Other solutions with more than 3 stages are possible.