Because 100 degrees is on the outside, that means the angle adjacent to it is 80 degrees. There are 180 degrees in a triangle, so that leaves 100 degrees left for the remaining angles.
(2x+11) + (2x+27) = 100
Combine like terms
4x + 16 = 100
Subtract 16 from 100.
4x = 84.
Divide.
84/4 = 21.
Therefore, x = 21.
