no of pupils in class 1 and 11 =3:5
no of pupils in class 1 and 11=7:11
(3:5)*7=21:35
(7:11)*5=35:55
if x:y,y:z=x:y:z like wise 21:35:55
a;b:c we can write as ax+bx+cx
like 21:35:55 we can write as 21x+35x+55x=333
x=333/111=3
so highest number of pupils in class=55*3=165
so ans is 165.