or
or
Student staying at the school is (100 - 20 = 80%) of the present students.
80% of the present students = 660
So, 100% or total present students = 660 x 100 / 80 = 825
But, present students = (1 - 1/12 = 11/12) of all enrolled students
Now, 11/12 of enrolled students = 825
So, all enrolled students = 825 x 12 / 11 = 900
