Illiteracy Isn't Always An Insurmountable Barrier

The other day I went to visit the mom of 2 boys and a little girl.
Janeth first came to our office for help a few years ago when her whole life, and that of her family, had been turned upside down.
Janeth was an illiterate wife brought from far distant area whose husband had given her HIV. At the time we met, the couple had just recently discovered their HIV status when the older boy became quite sick and was given an HIV test in the hospital. She was scared, dependent upon her husband (who'd started to drink) and unsure where to turn. Our counselor worked with the couple, obtained medical care for the boys, and things seemed to settle down.
Fast forward to yesterday.
After living for years on the small amount her husband makes as a butcher, Janeth has started a little business selling socks. She buys them in town and resells for a bit more in the market near her home. Janeth requested a bit of capital so that she can buy more at a time- and get a quantity discount.
 But how did she make change, keep track of money, since she cannot read, write, or do math and has never been to school?
Janeth told me she keeps track by selling her socks for 1,000 shillings each- fixed price, no bargaining. Tanzanian bills are in 1,000, 2,000, 5,000 and 10,000 notes, so she can easily keep track in her head according to the number of pairs bought and the bills exchanged. As long as she stays in base 10 (remember this from high school math?) she's fine.
Janeth seems empowered, loves having something that is all her own, and is proud of the progress her family has made. And the little surprise package on her lap? Karen is not infected and Janeth assured us that she now has permanent birth control in place.
Thanks for keeping me company. I'm headed home tonight!