A school held a math contest in which 80 students took part. The average score is 63, the average score of passing students is 72, and the average score of failing students is 48. How many students are there?

Suppose: X students pass and (80-x) students fail.

Equation: 72*X+(80-X)*48=80*63.

72*X+3840-48X=5040

X=50

That is, 50 people passed and 30 people failed.