You could represent your apple crate set like this...
Which shows that crate #1 has 5 apples, crate #2 has 7, etc.
November 30th 2009, 11:21 AM
You technically could use subscripts like the above poster said. He was using them to fit the situation you proposed. However I find using subscripts in this way confusing and not a common use. Subscripts are very useful in numbering the order of things, but not so much with the quantity of things. If A represents an apple, then you can just use multiplication to show more than one, i.e. 2A, 10A, etc.
My comments are about convention and how easy notation is to read by others.