Reshared post from +Christy Ramsey
Once you figure this out it'll blow your mind…
"The lines over the circles are color coded. Notice the single red line and 3 blue lines representing "13" grouped together while the single green and 2 black lines take their own group. [Simply] draw your first group of lines in one direction then your second group of lines going over the first, count the groups of intersections and there's your answer."
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