Answer: the required answer is 1320
Explanation:
Total people = 12
Different phone lines = 3
We will choose the person to answer the first phone in 12 ways.
Then choose the second person in 11 ways. (11 people left)
Then choose the third person in 10 ways. ( 10 people left)
The number of groups of 3 people can answer these lines
Hence, the required answer is 1320