YOU SAID:

There are 20 cats with 2 kittens, so now there are 40 cats

INTO JAPANESE

2匹の子猫と20匹の猫がいるので、今では40匹の猫がいます

BACK INTO ENGLISH

I have 2 kittens and 20 cats, so now I have 40 cats

INTO JAPANESE

子猫が2匹と猫が20匹いるので、今は猫が40匹います

BACK INTO ENGLISH

I have 2 kittens and 20 cats, so now I have 40 cats