Most apps would move on. But Cerebry flashed a second screen: Your Mistake Pattern . It showed Leo that his previous wrong answers all came from one habit—he forgot to perform the same operation on both sides of the equals sign.

“Leo,” the owl said softly, “you don’t have a ‘math problem.’ You have a ‘balance problem.’ Imagine the equals sign is the middle of a seesaw. Whatever you do to one side, you must do to the other. Got it?”

The Case of the Missing X

“See, Mia? You have to keep the equation balanced. It’s like sharing a pizza equally.”