The rule of the first test is that the previous number plus 4 equals the latter number. So it's19,23.

The rule of the second test is that the previous number MINUS 6 equals the latter number. So it's12,6.

The rules of the third test are complicated or problematic. First, the number rule of the middle circle is that the previous number plus 12 equals the latter number, so the third middle circle is 48. As for the number of ring parts. It can be said that the law can not be obtained by addition, subtraction, multiplication and division. A little deeper power calculation, etc. , can't be involved in the second grade.

If we think about it from another angle, according to the position of the number, the same ring position has appeared in front of us, which is 4/4/11,which is not obvious, because other ring positions have no particularly obvious laws to follow. But in the end, I will choose to fill in 4. This number is more likely.