Mr. Johnannsen has a farm with 3 cows, 8 chickens, and some ducks. If the total number of farm animals is 40, how many ducks does Mr. Johannasen have on his farm?

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