pusing gak ngerti tolong yg ngerti pake cara ya

EDG = 90
EFG = 90

80 + 30 + 90 + 90 + DEF = 360
110 + 180 + DEF = 360
DEF = 360 - 290
DEF = 70˚

sudut D sama F itu udah pasti 90° ya

∠GEF = 180 - (90 + 80) = 180 - 170 = 10°
∠GED = 180 - (90 + 30) = 180 - 120 = 60°

kedua sudut itu dijumlahkan, 10 + 60 = 70° (C)

semoga mudah dimengerti ^^