Check the clues in the case file one by one, and find the number in the lineup that matches every condition. Only one number satisfies all the clues.
The case file lists clues one at a time, like "this number is even" or "it's greater than 7." Cross off every suspect number that doesn't match a clue, and eventually only one number that fits every condition is left. This method of finding the answer by crossing off what it can't be is called the process of elimination.
For example, out of 12, 15, 18, 21, applying the clue "even" immediately crosses off 15 and 21, leaving only 12 and 18. Add the clue "greater than 15" and 12 gets crossed off too, leaving only 18. The game features clues like even/odd, multiples, digit sums, and remainders, and the middle-school difficulty adds primes and perfect squares for an extra challenge. This way of narrowing down candidates by checking clues one at a time is a genuinely useful habit for solving all kinds of problems.
🕵️ Pick the culprit (the secret number) from the lineup