An Unsolved Proof — David Cole

Hidden cameras, secret operations, and new math concepts await in the Math Kids' ninth adventure!

Justin has been accused of stealing from the comic book shop! To earn back the trust of his parents and the store manager, he'll have to work at the shop for four whole weekends. And that puts a damper on his plans to play video games and hang out with fellow Math Kids, Jordan, Catherine, and Stephanie.

With the end of summer approaching, the four friends realize that finding proof of Justin's innocence is their only way to save Justin's good name. To get it, they'll need to uncover who really stole the comics. Their primary suspects are the two older boys who accused Justin, but catching them red-handed will require more than just teamwork.

Solving this problem will require knowledge of proofs and patterns, and if the Math Kids aren't successful, it won't be just Justin's reputation at risk.