How to calculate the min number of intersections

When we have two line or two point and a number how to calculate the minimum possible number of intersections. By intersection i mean any possible point where two lines are intersecting each other or one point can be intersect with any number of lines. I need to pass this problem as soon as possible .<br><br><br>Example of cases<br><br> 2,7,2<br><br> 3,3,10