This is why the Japanese are better at math. Once you figure this out it'll blow your mind...

The lines and numbers above may not make any sense at first, but according to William C. at Themetapicture.com: "The lines over the circles are color coded. notice the single red line and 3 blue lines representing "13" group 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."