Here below is a data table:

To calculate the ranking of students by TotalScore (in descending order), and fill in the results in corresponding cell of column D, enter in cell D2:

=spl("=?1.conj().rank@z(?2)",C$2:C$12,C2)

Drag D2 down to every relevant row:

esProc Desktop and Excel Processing
10.9 Ranking of simple members
10.11 Ranking of row-based data - by combination of multiple columns