Respuesta :

Step-by-step explanation:

∠A + ∠B + ∠C = 180°

Here the value of ∠B and C is given below...we need to find the value of ∠A ....

a + 120° + 40° = 180°

a + 160° = 180°

a = 160° - 180°

a = 20°

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