For $2.50, you can purchase a waterproof, vinyl bumper sticker with any mathematical equation you like - 5x3, 11x8, 7x7 - any single combination you want, but only as high as 12x12, at least for now.

Hit the road in L.A., and you’re likely to spot a cheeky bumper sticker … or 17. As Times contributor Renée Reizman reports, the medium that was once popularized by Dwight D. Eisenhower’s ...