OK so if 70% of students in 8th grade have siblings and 112 8th graders have siblings, then:
0.7(total 8th graders) = 112
total 8th graders = 112/0.7
total 8th graders = 160
And since the number of 8th graders is 5/6 the size of the 7th grade class:
5/6(7th grade class) = 160
5(7th grade class) = 960
7th grade class = 192.
The correct answer is D) 192.
Hope this helps
cheers,
Brian
