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.