1) Consider that the 1st Quartile corresponds to 25%, the Median is equivalent to 50% of the data, the Third Quartile to 75% of the data as the sketch below:
Notice that the Median is that bar inside the box, also known as the 2nd Quartile.
2) So the percentage of the data greater than the median is:
[tex]75\%-50\%=25\%[/tex]