Q: There are nine points on a plane. No three points are in the same straight line. How many different triangles can be formed by using the nine points?
Q: There are nine points on a plane. No three points are in the same straight line. How many different triangles can be formed by using the nine points?
Assuming that the question means how many triangles are determined by those nine points then the answer is simply a combination of nine taken three at a time.