If you have to apply 40n of force on a crowbar to lift a rock that weights 400n, what is the actual mechanical advantage of the crowbar

The mechanical advantage is defined as the ratio between the force produced by a machine and the force applied in input:

For the crowbar of the problem, the force applied in input is 40 N, while the force produced in output is equal to the weight of the rock that is lifted, so 400 N. Therefore, the mechanical advantage is

The purpose of a lab is to do your "expirements" the importance of the topic is so you can now what the story is about and the last one is because no one is me with my question ( what is 3 over 4 x - 9 = 27 maybe you can )