Bob is phil's father. jack is phil's only brother. tina is phil's sister-in-law. phil is not married. mary is tina's mother-in-law. john is jack's son. what relation is john to mary? what relation is tina to bob? explain.

Because John is Jack's son, and Jack is Phil's brother, and Tina is Phil's sister-in-law, and Mary is Tina's mother-in-law . . . this makes John the grandson-in-law to Mary.  (note: it is possible that John is the grandson of Mary, but the relationship descriptions are not specific that Bob & Mary are married, so that deduction cannot specifically be made)

Because Tina is Phil's sister-in-law, and Phil is the son of Bob . . . this makes Tina the daughter-in-law to Bob.