On "Sesame Street," a distressed cow has a big problem. She made it up the stairs to the beauty parlor but now, her bouffant piled high, she's stuck. Cows can go up stairs, she moans, but not down.

PBS paired some of its greatest television talent for an entertaining new video aimed at solving some simple math. Presented with the problem by his "arch-nemisis" Murray-arty, "Sherlock" star ...