The mechanical advantage of a pulley system is calculated by dividing the output force by the input force.

In this case, the output force is equal to the input force, which is 3 N.

Therefore, the mechanical advantage is:

Mechanical Advantage = Output Force / Input Force = 3 N / 3 N = 1

This means that the pulley system doesn't actually provide any mechanical advantage. It simply changes the direction of the force, not its magnitude.