The central angle with vertex at the center of the Earth is : α = 12` = 1/5° = 0.2°.
The distance between two islands:
L = R π α / 180°
Earth radius = 6,317 km = 3,959 miles
L = 3,959 · 3.14 · 0.2° / 180°
L = 13.82 miles
Answer: Two islands are 13.82 statute miles apart.