The geographic occurrence of a paired oceanic trench and island arc system indicates

A volcanic island and about 200 km from a volcanic arc.

Explanation:

The occurrence of the volcanic island that s located about 200 km of the trench system indicates the forms of the mid-oceanic ridges that are consistently found in the latitudes that are dominated by the islands arc and mostly found in the pacific oceans and these are thus also the geologic occurrences and hence are found in pairs.

H=   2(area/a+b)h= 2(144/a+b)h= 2(144/18+18)h= 2(144/36)h= 2(4)h=8