∵ 100× 13= 1300< 1392,
∴ The number of people in Group B is not less than 50 and not more than100;
(2) Form two tour groups, A and B, with X and Y people respectively.
Then13x+11y =1392.
9(x+y)= 1080。
Solution: x=36
y=84。
Or13x+11y =1392.
1 1(x+y)= 1080。
The solution is x= 156.
Y=-636/ 1 1 (irrelevant, omitted)
A: There are 36 and 84 tour groups A and B respectively.