Question

a group of students attend a math class half of the students are boys and four ninths of the boys have brown eyes what fraction of the groups are boys with brown eyes

Answer 1

Group of students = 18/18 (100%)
Boys = 9/18 (50%)
Boys with brown eyes = 4/18 (idk :p)

It's 4/18 because:
Brown eyed boys make out the 4/9 of the boys, and boys make out the half of the whole class. So the easiest way was to double 9 and get x/18. (Sorry for my bad English..)