[jakethebake]

If you've run a half marathon, this is doable. Just run a couple of 5-milers during the week and extend a long run on the weekends over the next three weeks. For example:

Week 1 - Mon: 5 mi. - Wed: 5 mi. - Sat. 15 mi.
Week 2 - Mon: 5 mi. - Wed: 5 mi. - Sat. 18 mi.
Week 3 - Mon: 5 mi. - Wed: 5 mi. - Sat. 22 mi.
Week 4 - Mon: 5 mi. - Wed: 5 mi. - Sat. Marathon