Complex sentence: Mazahua girls as young as four learned how to run an onion stand by sitting with their mothers and other women, observing and participating in the business, often by getting change for customers at other market stalls.
Split into simpler sentences: Mazahua girls as young as four learned how to run an onion stand by sitting with their mothers and other women. These girls observed how their mothers ran the business and began to participate by getting change for customers at other market stalls.