21.   But watch out if they tackle a math problem.

22.   Discusses a math problem with father, reviews notes for sixth-grade history quiz with mother.

23.   Dr. Ed Witten, who worked on complex math problem with Dr. Nathan Seiberg.

24.   Eats yogurt while discussing a math problem with son.

25.   Everything she thinks of, every experience she has, turns into a math problem.

26.   For a few weeks, she will put aside her math problems and take walks and read.

27.   Gonzales would break pieces of the chalky paint and use them to write math problems on a wool blanket.

28.   He earned his Ph.D. by solving, in less than a year, a math problem that Piranian himself had been unable to solve.

29.   He must answer a series of math problems to get his guy through the rooms of the pyramid and out.

30.   His sheet of math problems is clipped to an angled tray attached to his wheelchair.