42-X = 75%(X+28)
42-X = 75% X+2 1
42-X-2 1 = 75% X
2 1-X = 75% X
2 1 = 175% X
X = 12 ... boys.
X+28=40 (person) ... girl.
(40+ 12)/ 2/5= 130 (person) ... the total number of sixth-grade students.
A: There are 130 students in the sixth grade.