The question is an illustration of arithmetic sequence.
<em>The number of conversation for 19 people is 171</em>
<u />
<u>(a) 9 people</u>

9 represents the number of people
8 represents the number of conversation each person had
2 represents the number of people having a conversation at once (i.e 2 people at once)
<u>(b) 19 people</u>
We have:

The number of conversation is:

So, we have:




Hence, the number of conversation for 19 people is 171
Read more about arithmetic sequence at:
brainly.com/question/18109692
12 divided by 3 is 4. the answer would be 40 as 4x10 is equal to 40
Answer:
The student made the first mistake in step 2.
Step-by-step explanation: