<h3>Answer: approximately 6.3 miles</h3>
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Explanation:
See the diagram below. The two given angles B = 105 and C = 20 are used to help find angle A
A+B+C = 180
A+105+20 = 180
A+125 = 180
A = 180-125
A = 55
Then we use the law of sines to find the side length c
sin(A)/a = sin(C)/c
sin(55)/15 = sin(20)/c
c*sin(55) = 15*sin(20) ... cross multiply
c = 15*sin(20)/sin(55) .... divided both sides by sin(55)
c = 6.26294249724791 .... value is approximate
c = 6.3 ....... rounding to one decimal place