bearing in mind that the sum of all interior angles in a polygon is
180(n - 2) n = number of sides in the polygon
a DECAgon, DECA=10, has 10 sides, and thus the sum of all its interior angles is 180(10 - 8) = 1440.
[tex]\bf 156+135+147+160+116+150+150.2+119.2+146.6+z=1440 \\\\\\ 1280+z=1440\implies z=1440-1280\implies z=160[/tex]
