The Triangle SecretPaperback, 1 April 2022

When FBI Special Agent Carlson is kidnapped in Egypt while investigating the plane crash of an eccentric billionaire inventor, Jordan and his friends spring into action. Catherine, The Math Kids must unravel the clues in Howell's mysterious will before it's too late. If they can't figure out the secret of the triangle in time, Howell's money will be gone forever.

Now the Egyptians are after the Math Kids, too. In their most exciting adventure to date, the four friends will need all their math skills to save their FBI friend and find the missing money.