Numbers not in math mode

[twjudson]

Numbers relating to math that aren't in math mode end up in the oldstyle numerals. I'm sure I don't have a complete list (perhaps there would be some easy way to search the XML?). For example, in figures 1.7, 1.9, 5.22, 5.23, 19.7, examples 4.5, 4.6, exercise 7.2.c.