There are 20 straight lines in a plane so that no two lines are parallel and no three lines are concurrent. Determine the number of points of intersection.

In how many points do two lines intersect ?

Observe the figure given below. Name concurrent lines

The equation of straight line passing through the point (a,b,c) and parallel to Z-axis, is:

What are names of horizontal and vertical lines drawn to determine the position of any point in plane?

There are n points in a plane. Find the number of straight lines that can be obtained by joining points if a) no three points are collinear. b) p points are collinear.