Let the total number of children be 'x'
So, the number of gifts each child will get = x-1 (He will not gift himself, that's why one less)
So, total number of gifts = x*(x-1)
x²-x = 132
x²-x-132 = O
So, x= 12, -11
Now, the number of children can't be negative.Therefore, number of children is 12.
Hope it helps !!!