There are 42 cats, and 49 dogs at animal shelters because I know that 6:7 will have total 13 parts, and I just need to take 91 divided for 13 to get 7 for each part, and to find how many cats are there; I just need to take 7 times 6 to get 42 cats, and take 91 subtract for 42 to get 49 dogs. Hope it help!