Answer:
14%
Explanation:
If the percentage of boys wearing polo shirts were boys, then the rest has to be girls. So 100%-80%=20%. However, we are not done here.
We have only figured out the percentage of girls out of the total number of people wearing polo shirts. We want to find the percentage of girls wearing polo shirts out of the whole school. To do that, we multiply 20% by 70%, since 20% of the polo shirt wearers were girls, and 70% of the entire student body is wearing a polo shirt.
Multiplying those two together gets you 14%.