Ask how many bugs each bird eats every day: 229.5/6=38.25.
Second, ask the four birds how many bugs they eat every day: 9 18/6= 153.
Ask how many bugs each bird eats every day: 153/4=38.25.
The third type: solve by equation.
Suppose every bird eats X worms every day: 4*x*6=9 18.
The solution is x=38.25.