question: List the position of players with average number of points scored by players of that position bigger than 20.
#1 return players  
#2 return positions of   #1 
#3 return points scored by #1 
#4 return number of  #3 for each #1 
#5 return the  average of   #4 for each #2 
#6 return #2 where #5 is  bigger than  20