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Step-by-step explanation:

For a parallelogram the diagonals (and half diagonals are equal. So we can say

3m=m+8

2m=8

m=4

And we can also say that

3m+m+8=2n-1+9

4m+8=2n+8

4m=2n

2m=n, and since we know m=4

n=2(4)

n=8

So m=4 and n=8

 6.71, if you round it, it would be 7. To solve the problem, I used the the ‘arc formula.’