Let us place the data in ascending order (smallest to largest)-
[tex]\longrightarrow[/tex]90 ,98 ,98 ,99 ,100 ,100
Since the given data has even set of numbers, we will have to find two numbers in the middle-
[tex]\longrightarrow[/tex] 90, 98, 98 ,99 ,100 ,100
Add the two middle numbers and then divide by two, to get the average,which is our median:-
[tex]\begin{gathered}\\\implies\quad \sf 98+99 = 197\\\end{gathered} [/tex]
[tex]\begin{gathered}\\\implies\quad \sf 197/2 = 98.5 \\\end{gathered} [/tex]
[tex]\leadsto[/tex]Thus the median of given set of data is 98.5
Note - In case of odd sets of numbers, there is only one middle term which is median.