Final answer:
The two correct sentences using hyphens are A and B.
Step-by-step explanation:
The two sentences that use hyphens correctly are:
A. My neighbors had a dog that was friendly-looking.
B. The ballroom in the hotel can accommodate about 300-350 people.
In sentence A, the hyphen is used to connect the words 'friendly' and 'looking' as a compound adjective. In sentence B, the hyphen is used to indicate a range between the numbers 300 and 350.
Learn more about Hyphens in sentences