In a plane,there are $10$ points,out of which $4$ are collinear. The number of triangles that can be formed by joining these points is:

In how many ways can $5$ boys and $5$ girls stand in a row so that no two girls may be together?

On an $n \times n$ chessboard,the total number of rectangles which are not squares is $350$. Then,the number of white squares on the chessboard is .......

If all the six-digit numbers $x_1 x_2 x_3 x_4 x_5 x_6$ with $0 < x_1 < x_2 < x_3 < x_4 < x_5 < x_6$ are arranged in increasing order,then the sum of the digits in the $72^{\text{th}}$ number is $............$.

In a row,$6$ boys and $6$ girls are arranged at random. Find the probability that all $6$ girls are together.

Find the number of marked points on the plane,if when connected pairwise by line segments,the total number of line segments formed is $15$.