Of the cats at a cat show. were black and were white. The rest of the cats were brown. What fraction of the cats show were brown? I need help me please

The fractions have a denominator of 7.
All the cats would need to equal 7/7 which would be 100%
Subtract the amount of black and white cats from 7/7
7/7 - 2/7 = 5/7
5/7 - 3/7 = 2/7
2/7 of the cats are brown