Multiple Representations is the idea that a physical phenomena can be explored in many different ways. For example, there is the physical representation which models the system with figures and diagrams, such as a free body diagram. There is also the mathematical representation which uses the equation(s) governing the physics of the system. All of the representations can be used together to help us understand and quantify the physical phenomena.

 

Observe the different types of representations for this section below;

Physical Representations explain the features of the situation in a visual way, often with vector representations of physical quantities overlaid a simple diagram or picture of the situation.

Mathematical Representation uses equation(s) to describe the situation.

This site has great step by step caluclations for MA.

Graphical Representation describes the situation through use of plots and graphs.

A graph of three ramps at different angles plotting the force required to lift an object, unaided, vs lifting the object with the ramp.

Descriptive Representation is made up enitrely of words or annotations. Think about how you might explain the situation to someone else.

I am trying to life a box that weighs 600 N. I can only lift 150 N as I don’t even lift bro. However, the physics is strong with me and I know that I can use a pulley system like the one in the physical representation section above. 

 
Actual Phenomena could be thought of as doing the experiment. For example, if you're asked which of two runners, with different characteristics of their speeds, will win the race, one way to determine that would be to get two runners to run in the described way and see who wins.

This video is good example of Mechanical Advantage;

Also this video shows a man using MA to pull his truck;