a small island has 2/5 of its surface covered by forest and 1/4 of the remainder of its surface by sand dunes.The island also has 90 hectares covered by farm land if the lsland is made up of only forest.what is the total area of the island.
问题描述：
a small island has 2/5 of its surface covered by forest and 1/4 of the remainder of its surface by sand dunes.The island also has 90 hectares covered by farm land if the lsland is made up of only forest.what is the total area of the island.
答