So to work out how many women there are in the class you would have to:
26 - 16 = 10
As a fraction this would be 10/26.
You may be asked to simplify so to simplify you need to work out what number goes into both numbers this would be 2.
10 ÷ 2 = 5
26 ÷ 2 = 13
So 10/26 is the answer and if simplified it would be 5/13.