Answer:
![N_3=(T_1)/(T_3)N_1](https://img.qammunity.org/2020/formulas/engineering/college/mse2ltl298ef57lvd0temzhpznps8yhzd4.png)
Step-by-step explanation:
In the diagram there three gears in which gear 1 is input gear ,gear 2 is idle gear and gear 3 is out put gear.
Lets take
![Speed\ of\ gear 1=N_1](https://img.qammunity.org/2020/formulas/engineering/college/eact6b9ioisoh5nopiquhh8yemqthb3qee.png)
![Number\ of\ teeth\ of\ gear 1=T_1](https://img.qammunity.org/2020/formulas/engineering/college/5imu0nk419hhuo7cq9qrczda4go2yoopyp.png)
![Speed\ of\ gear 3=N_3](https://img.qammunity.org/2020/formulas/engineering/college/4ya8ftgu8pjvh0vw50eor8wp05el14oj1a.png)
![Number\ of\ teeth\ of\ gear 3=T_3](https://img.qammunity.org/2020/formulas/engineering/college/t1ng5jyieih661x228ow400fwvr22pws71.png)
All external matting gears will rotates in opposite direction with respect to each other.
So the speed of gear third can be given as follows
![(T_1)/(T_3)=(N_3)/(N_1)](https://img.qammunity.org/2020/formulas/engineering/college/lsgawd9mglj6nilxaz1tel4nqmo0or7goo.png)
![N_3=(T_1)/(T_3)N_1](https://img.qammunity.org/2020/formulas/engineering/college/mse2ltl298ef57lvd0temzhpznps8yhzd4.png)