How to clear the lowest 10 values from a list of 30 values

Suppose I have a database of 50 students. Each row starts with the name of the student and then marks of 30 quizes for each student. e.g.-

Jack- 10 7 8 5 10 9 8 7 3 6 4 7 3 ........
Millie- 2 3 10 9 8 2 7 1 2 9 2 0 7 9.......
Ryan- 4 5 7 8 9 10 2 4 5 7 8 9............
...............................................................
..............................................................
Now I want to count only best 20 quiz marks out of 30 quizes and show the cells containing 10 lowest values as blank.
e.g. if i want to clear lowest 5 values for jack-
Jack- 10 7 8 _ 10 9 8 7 _ _ _ 7 _ ....

Now how do I do this and how do I repeat it for all 50 students? That is, how do I show only best 20 quiz marks out of 30 for each student?


please help
fap87