Hello, look at the answer to this question first and find that these figures are very small. At this time, you should be laughing. This small number should be shot one by one ~ ~ but don't write one by one unless you have to, it's easy to miss the shot ~ ~ ~ so the method should be mastered! The following is the answer process:

Because a is a, yes, b and c are not in c,

The first step, assuming that both B and C are in B, then the remaining three people are in A and the other two are in C, then jump out of three people and put 1 in A to be 3C 1 (this is the combination number, and 3 is marked in the lower right corner of C), and the other two people can only be put in C.

Step 2: If B is in A and C is in B, then one of the remaining three people will jump out and put B, and the remaining two will put C, which is 3C 1.

The third step, because B and C are equivalent, is 3C 1 just like the second step.

To sum up,1* * is three times that of 3C 1, that is, 9 ~ ~ ~

Honey, do you understand? Plus points ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~