Question

A machine is designed to lift an object with a weight of 12 newtons. If the input force for the machine is set
at 4 newtons, what is the mechanical advantage of the machine?

Answer 1

Mechanical advantage is calculated by output force/input force (Fo/Fi).

So, 12/4=3.

Answer 2

If the input force for the machine is set at 4 newtons, then the machine
may or may not be able to lift the object.  If it IS able to lift an object that
weighs 12 newtons, then the mechanical advantage of the machine must
be at least  3  or more.