Answer:
Third grade secondary = 87 students
Explanation:
First grade = 30/100 x 250 = 75 students
Second grade = 35/100 x 250 = 87.5 rounded off to 88 students. Because students can't be half thus can't be in decimal. So round off to the nearest whole number.
Third grade = 250 - 88 - 75 = 87 students