Lets Make a Deal Mike and his little brother, Andy, are headed for the Dinosaur Card Trading Fair. They're ready to wheel and deal. It's, 4 "Stegosaurus" for 1 "Triceratops," and 2 "Triceratops" for 1 "Allosaurus." But can they get what they really want: the tremendous, gigantic, ferocious, "Tyrannosaurus rex"? The math concept of equivalency -- understanding when values are equal -- is introduced in this fast-paced story as two brothers try to beat the clock and make the ultimate trade.