90xn/(60+90+m) = number of people drawn from Group B.

The number of people drawn from group A is one less than that drawn from group B.

30Xn/(60+90+m)= 1

60Xn/(60+90+m)=2

When m=30, n=6.

Mathematical expectation and average probability of distribution table?

A total of ***6 people were sampled and 3 people paid a return visit. Some people are on team A, and the distribution list is X (no team A) 0% X (with one team A) 33.3% X (with two teams A) 66.6%.

The mathematical expectation is 1/3.