tolong jawab ya kak, kalau bisa sama caranya

120° + b° = 180°
b° = 180° - 120°
b° = 60°

60° + a° = 180°
a° = 180° - 60°
a° = 120°

B = 180 derajat - 120 derajat
B = 60 derajat

180 derajat - 60 derajat =120 derajat