<span>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.</span>
The other one (number2) is not a function, because if you plot those points in a graph and use the line rule it shows that more than one point is aligned in that line.
