To distribute the numbers from 1 to 9 into the nine circles such that the sum of the numbers on each of the three sides of the triangle is 20. The diagram shows a triangular arrangement of circles, wi

The problem asks to distribute the numbers from 1 to 9 into the nine circles such that the sum of the numbers on each of the three sides of the triangle is 20. The diagram shows a triangular arrangement of circles, with some numbers already filled in. However, as shown in the thought process, the pre-filled numbers do not satisfy the condition. We need to find a correct distribution.

Let the three corner circles be $C_1, C_2, C_3$.
Let the two middle circles on the side between $C_1$ and $C_2$ be $M_{1a}, M_{1b}$.