YOU SAID:

there were 30 cows and 20 ate chickens how many didn't?

INTO JAPANESE

30頭の牛と20頭の鶏がいませんでした。

BACK INTO ENGLISH

There were 30 cows and 20 chickens.

INTO JAPANESE

牛は30頭、鶏は20頭でした。

BACK INTO ENGLISH

There were 30 cows and 20 chickens.