Answer:
87+87+81+86+89+83+89= 602. Divided by 7 because that’s how many numbers there were is 86 and that is your mean/average.
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9( n - 4 ) - 4n ( n - 4 )
We can take ( n - 4 ) as common as both are getting multiplied by ( n - 4 )
We can join 9 - 4n together
Therefore, the final answer will be ( n - 4 )( 9 - 4n )