jawab+cara plis bsk dibwa! thanks yg udh jwab

Maaf cuma bisa yg no. 3 :((

a. 6x + 2x + x = 180°
9x = 180°
x = 180° : 9
x = 20°

b. 2x + 3x + 90° = 180°
5x = 180° - 90°
5x = 90°
x = 18°

c. 2x + 3x + 4x = 180°
9x = 180°
x = 180° : 9
x = 20°

d. 2x + 3x + x = 180°
6x = 180°
x = 180° : 6
x = 30°

Maaf kalau ada yg salah :)