4 ? 9 ? 2

3 ? 5 ? seven

8 ? 1 ? six

This picture adds up to 15.

One person wears nine shoes, three on the left, seven on the right, two on four shoulders and six on eight shoulders.

Nine palaces of mathematics: the sum of the numbers on the vertical and horizontal diagonal lines is fifteen.

That is to say, 123456789 is divided into three lines, nine and one in the middle of the first and third lines, seven and three in the left and right of the middle line, two and four in the left and right of the first line, and six and eight in the left and right of the third line. Five is in the middle.