Question 1143913
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Think about it ... imagine drawing the lines one at a time:

The first line has no lines to cross.  Common points = 0.

The 2nd line can cross the first line (at most) once.  Common points = 1.

The 3rd line can cross each of the first two lines once.  That's two more.  Common point count is now 1+2 = 3.

The 4th line can cross each of the first three lines once.  That's three more. Common point count is now 3+3 = 6.

B) 6