Question 565199
The U stands for union, meaning a set that has all the elements of both united sets.
AUB={1,2,3,4,5,6,7}
The upside down U means intersection, meaning the set of elements common to both sets. The intersection of A and B is {3,4}.
{{{drawing(300,200,-10,10,-6,6,
red(circle(-3.5,0,5.5)),
blue(circle(4,0,5)),
locate(0,1,3), locate(0,-1,4),
locate(-8,0,5), locate(-4,2,6), locate(-4,-2,7),
locate(3,0,1), locate(6,0,2)
)}}} The red circle represents set A. The blue circle represents set B.