besar sudut BFG adalah

(4x+30) + (3x+10) = 180
4x + 3x + 30 + 10 = 180
7x + 40 = 180
7x = 180 - 40
7x = 140
x = 140/7
x = 20

jadi sudut BFG adalah....
4x + 30 = 4(20) + 30 = 80+40 = 120 derajat

(4x + 30)° + (3x + 10)° = 180°
(7x + 40)° = 180°
7x = 180° - 40°
7x = 140°
x = 20°
sudut BFG = (4x + 30)°
= (4 (20) + 30)°
= (80 + 30)°
maka sudut BFG = 110°