In a test taken by 400 students, Meera's score is at the 85th percentile. How many students scored MORE than Meera?

Being at the 85th percentile means 85 percent of the students scored at or below Meera, so 100 − 85 = 15 percent scored more than she did. That is $0.15\times 400=60$ students. The value $340=0.85\times 400$ is the number at or below her, the group she has beaten rather than the group ahead of her. The value 15 is the percentage itself, left unconverted into a count of students — a percentile tells you a POSITION in the data, and it must be turned into a head count before it answers a 'how many students' question. The value 85 is the percentile label read as though it were a number of students, which would leave the size of the test group unused altogether.