Aveterinarian treated 7 dogs, 13 cats, 4 horses, and 3 ferrets. what percentage of his patients were small animals?

As per your defention, horses are the only thing considered "not small".  To find the percentage, you take the number of what you are trying to find the percentage of divided by the total number.

So, 7 dogs + 13 cats + 3 ferrets = 23 Small animals

7 dogs + 13 cats + 3 ferrets + 4 horses = 27 total animals.

So,

The reason we multiply by 100 is because the division gives us a decimal, and a percentage is a part out of 100.

So by doing the calculation we get

85.18%

it is 10.6 according to my calculations