Teaching Assistants = TA
Students = S
Let assume the ratio of TA/S = 3/80 (Just putting aside the requirement it must be greater)
Let say x be the maximum no of students possible with 5 teaching assistants = 3/80 = 5/x
x = 400/3 = 133.3.
. Now for ratio to be greater than 3/80, we will have to reduce the denominator.
Let us just round it to lowest integer as number of student cannot be a decimal.
The new ratio is 5/133, which is less than 3/80 and hence 133 is the max number of the students.