Mean = average of the numbers of the set and
Median (after arranging the set in ascending order)
is middle number if the number of elements in set are odd
or average of middle two numbers if the number of elements are even

In this question the number of elments in the set is 10

Mean = (40+45+45+50+50+60+70+75+95+100)/10 = 630/10 = 63
Median = (50+60)/2 = 55.

So u need to tell how many scores are between 55 and 63 i.e 1

Whoa! Thanks much! I was making the mistaking that this was an odd set and thought the mean equaled the median.

Just a warning/caution:

Even in odd set one can't say whether mean and median are same or not without calculation..