Сумма смежных углов равна 180°.
∠RTS + ∠STM = 180°
∠RTS = 180° − ∠STM
Сумма углов треугольника равна 180°.
∠S + ∠T + ∠R = 180°
∠R = 70°
∠STM = 2∠S
∠S + ∠T + 70° = 180°
∠S + ∠T = 110°
∠S + ∠STM = 180° − 70°
∠S + ∠STM = 110°
∠T = 180° − ∠STM
∠S + 180° − ∠T = 110°
∠S + 180° − 2∠S = 110°
−∠S = −70°
∠S = 70°
∠STM = 2 × 70° = 140°
∠STR = 180° − 140° = 40°
Ответ: ∠S = 70°, ∠STR = 40°