pada gambar diatas,nilai x =

a = sudut di dalam segitiga (yg belum diketahui)

180 = a + 70 + 50
a + 120 = 180
a = 60°

180 = 4x + 20 + 60
4x + 80 = 180
4x = 100
x = 25

(70°+50°)-180°
=120°-180°
=60°

Nilai x
4x+20°+60°=180°
4x+80°=180°
4x=180°-80°
4x=100°
x=100°/4
x=25°