Answer: 5/12 of the school's students are in eighth grade.
Step-by-step explanation:
The three grades in Kyle's middle school are sixth, seventh, and eighth.
One-third of the students are in sixth grade and one-fourth are in seventh grade. This means that the total number of students in sixth grade and seventh grade would be
1/3 + 1/4 = (4 + 3)/12 = 7/12
Therefore, the fraction of the school's students that are in eighth grade would be
1 - 7/12 = 5/12
