Answer:
d = 4[m]
Step-by-step explanation:
Torque in physics is defined as the product of force by distance. This way you can use the following equation to calculate the torque.
![T=F*d](https://img.qammunity.org/2022/formulas/physics/high-school/lmj9wsuuqdkfk06p06e67z4np7dumjklow.png)
where:
T = torque [N*m]
F = force [N]
d = distance [m]
Now replacing in the equation above.
![84=21*d\\\\d= 4[m]](https://img.qammunity.org/2022/formulas/physics/high-school/eut2c1sqpbpirrdhwz30rx36i3cf8n4ll8.png)