1, the proportion of students in grades 2 and 3 is 12: 15: 16.
430/( 12+ 15+ 16)= 10
Grade one: 10x 12= 120.
Grade two: 10x 15= 150.
Level 3: 10x 16= 160.
160- 120=40 (person)
I'm only in the sixth grade. I hope it helps you.