The following is a hand drawn experiment, however, i believe it would best be received if the educators actually used a scale and a real doggy-bowl(or a paper bag) on both sides to represent the variable as well as actually manipulated the experiment so as to show how the scale must balance. Thus, i'm well aware that the hand drawn experiment here is flawed...but i think you'll get the idea :)
How Many Bones Are In The Dog Bowl
Use Algebra To Solve
Now look in the dog bowl to see if you are correct?