Circle 1 according to the above picture. The number of the left half is 5+5+1=1,and the number of the upper half is 5+5+2= 12. Right half number 2+5+7= 14 lower half number 1+5+7= 13.

By analogy, the second circle, the third circle and the fourth circle are the sum of three numbers calculated from left to right.

The last circle can be inferred from this. 1+9+ 1= 1 1.

Fill in 9, 1 1, 14 in the middle, then you can calculate 9+4+ 1= 14, so fill 4 in the lower left.