Mark, the little Minus Sign In the sweetest book that ever was written about math, Mark, the little Minus Sign, is on the adventure of a lifetime-and the story problems he solves are just the half of it. He's also learning about growing up: making friends and finding his own unique talents. The youngest of readers, ages four to six, will love the story of Mark who is not so different from them-which will help prepare them for encountering their world...