Answer to three friends each create 4 bags of starter bread dough. After ten days, each of those four bags is then divided into four more bags of dough. How many days pass before 192 bags of dough are created

To begin, each of the friends have made 4 bags of dough. This gives 12 bags at the outset. After 10 days, all 12 bags are made into (4*12) bags, or 48 bags. After 20 days, the 48 bags are made into (48*4), or the required 192 bags. After 20 days, then, the friends have the needed 192 bags.