Ahodges/doc/doc1117

@mulby , @shnayder , @WatsonEmily , @mhoeber , @catong , @srpearce , @stroilova , @dsjen please review. I do not yet have images to illustrate my examples, but otherwise ready.
You can see columns named *Age*, *Total Enrollment*, and *Percentage*.

or

Columns show each age, along with the total enrollment and percentage for each age.

or

You can see a row for each age. You also see a *Total Enrollment* column and a *Percentage* column for each age.

or similar