21 is the key
Warlin was used to being bothered by his pesky younger brother, Twerpin. But this time his brother had gone too far. Warlin muttered to himself, "When I catch Twerpin, I'll teach him a good lesson for putting this weird lock on my bike. What am I supposed to do? The lock has thirteen hollow circles connected by lines. There are thirteen clay numbers lying on the ground: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13."
Just then Buba, Twerpin's dog, came over and gave Warlin a wet lick across his face. Warlin was about to push the dog away when he noticed a piece of paper tied to its neck. He grabbed the paper. It was a message from Twerpin. Warlin read it out loud, "Hi big brother. Having a little trouble with a lock. Why don't you try putting one clay number in each circle? Do it in a special way. The total of the three numbers in each line of three joined circles has to equal 21. When you have a total of 21 in every line of three circles, the lock will open. A nice problem, eh!"
Just then Buba, Twerpin's dog, came over and gave Warlin a wet lick across his face. Warlin was about to push the dog away when he noticed a piece of paper tied to its neck. He grabbed the paper. It was a message from Twerpin. Warlin read it out loud, "Hi big brother. Having a little trouble with a lock. Why don't you try putting one clay number in each circle? Do it in a special way. The total of the three numbers in each line of three joined circles has to equal 21. When you have a total of 21 in every line of three circles, the lock will open. A nice problem, eh!"
Warlin crumpled the paper and threw it as far away as he could. Then he looked at the lock and began to think.
