The question is an illustration of arithmetic sequence.
<em>The number of conversation for 19 people is 171</em>
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<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
 
        
             
        
        
        
Answer: 7
Step-by-step explanation: 
 
        
             
        
        
        
Answer:
42 yards
Step-by-step explanation
There are 4 sides to a rectangle. 2 lengths, and 2 widths. That means that you multiply both values by 2 and then add them together, so 40 + 2. A more basic way to think of it is 20+20+1+1. Therefore, the perimeter is 41 yards. 
 
        
             
        
        
        
Answer: you minus the equations you have to get the equation that you want so it all can add up to that *
Step-by-step explanation: