m∠F, m∠D and m∠G have to be 180° together in order to form a triangle So m∠G = 180° - 2×40° = 100° One line is cutting m∠G in half and we get m∠EGF and m∠EGD We want to know how much m∠EGF is so... m∠EGF=100°÷2=50°
Now we have m∠F which we can name m∠EFG and we have m∠EGF Together with m∠FEG they form a triangle so that means together they have the value of 180° m∠FEG=180°-40°-50°=90°
