The number of diagonals that can be drawn in an octagon is

Seven white balls and three black balls are randomly placed in a row. The probability that no two black balls are placed adjacently equals

How many parallelograms can be formed by a set of $4$ parallel lines intersecting another set of $3$ parallel lines?

There are $10$ points in a plane,out of which $6$ are collinear. If $N$ is the total number of triangles formed by joining these points,then $N=$

The number of diagonals of a polygon is $35$. If $A$ and $B$ are two distinct vertices of this polygon,then the number of all those triangles formed by joining three vertices of the polygon having $AB$ as one of its sides is:

In a plane,there are $37$ straight lines,of which $13$ pass through the point $A$ and $11$ pass through the point $B$. Besides,no three lines pass through one point,no line passes through both points $A$ and $B$,and no two lines are parallel. The number of intersection points the lines have is equal to: