Very simple, 13 people. Analysis: There are ***x people in the group, and everyone gives gifts to each other, so everyone gives x- 1 cards and * * * gives x*(x- 1) cards. Column equation: x*(x- 1)= 156, solve the equation to get x= 13 or x=- 12 (the number of people cannot be negative, so it is omitted), so x= 13 (people).