First, apart from using the assumption method, the units drawn for men and women should not be assumed equal as the question did not state so. You may have confused her thus. Next, there would be a total of 8 units after subdividing the two units drawn for women, how is the 10 units being arrived? You may have confused her further. Last, you did not make use of any of these three pieces of information given : 3/4, 50% and 80 more. How could she not be confused?