Answer:
29
Step-by-step explanation:
The total number of animals is ...
(number of cows) + (number of chickens) + (number of ducks) = (total)
Filling in the given numbers, we have ...
3 + 8 + (number of ducks) = 40
Subtracting 11 from both sides of this equation gives us ...
number of ducks = 29
