36992

There are 10 points and nine lines coming from every point. The first point will have nine lines, the second eight as it already has a line from the first one, the next 7, then 6 and so on...
Then 9+8+7+6+5+4+3+2+1=45, so there are 45 lines altogether.

Another, less accurate way of working this out is to do 9 lines x 10 points = 90. But as every line joins 2 points, you do 90 divided by 2 = 45 as well.