Supplementary angles are angles that are adjacent to each other and when summed to get a total of 180 degrees. In this case, DEF and FEG are supplementary. Thus the equation is 9x +1 + 8x + 9 = 180 = 17 x + 10; x then is equal to 10 so
<DEF = 9*10 +1 =91 degrees
<FEG = 8*10 + 9 = 89 degrees
