Sinkholes are just one of many forms of ground collapse, or subsidence. Land subsidence is a gradual settling or sudden sinking of the Earth’s surface owing to subsurface movement of earth materials. The principal causes of land subsidence are aquifer-system compaction, drainage of organic soils, underground mining, hydrocompaction, natural compaction, sinkholes, and thawing permafrost. Land subsidence can affect areas that are thousands of square miles in size.
Because when you add 27 and 39 together you get 66. And the interior of a triangle equals 180 so now you must subtract the 66 from 180. And once you do that you get 114 degrees.
