Answer: The distance between port 3 to port 1 is 7.7 miles.
A rough sketch is attached.
The angle between 3.5 and 6 is = (90 + 15) = 105 degrees.
We will need the law of cosine.
So the distance between port 3 to port 1 is:
[tex]\sqrt{3.5^{2}+6^{2}-2\left(3.5\right)\left(6\right)\cos\left(105\right)}=7.68897911912=7.7[/tex].
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