Answer:
-54
Step-by-step explanation:

Multiply 8 by -9 and 6 by -3

Subtract
Hope this helps
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Answer:
n=3
Step-by-step explanation:
Operation used is division
The mean is all of them added together divided by the number, so multiple the mean by the number of sides, 3, and that's the perimeter. 18 x 3 = 54