There were 64 people with brown eyes and black hair; that makes the percentage of the population 64/303 = 21.12% ≈ 21%.
There were 9 people with blue eyes and black hair; that makes the percentage of the population 9/303 = 2.97% ≈ 3%.
This means the percentage of students with brown eyes and black hair was greater than the percentage of students with blue eyes and black hair by: 21-3 = 18%.
