In decipher jumbled up description type of questions, a round-about description is given in the form of certain small relationships and direct relationship between the persons concerned is to be deciphered.
Introducing a man, a woman said, "He is the only son of my mother's mother."
How is the woman relatedto the man ?
My mother's mother -- My grandmother;
My grandmother's only son -- My maternal uncle.
So, the woman is man's niece.