bedasarkan gambar di atas, nilai x + y adalah

garis A ke C = 180°
2x + 70 + 90 = 180°
2x = 180 - 160 = 30
x = 30/2 = 15°

70 + 90 + 3y - 4 = 180
156 + 3y = 180
3y = 180-156 = 24
y = 24/3 = 8°

x + y = 15+8 = 23°