Answer:
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Step-by-step explanation:
Let us assume A, B, C and D are the four angles of the parallelogram. Where, ∠A = 20° and we have to find the measure of ∠B, ∠C and ∠D
So, If ∠A = 20°, then So, also ∠C = 20°.
Therefore,
⠀
And, ∠A and ∠B are adjacent angles. We know,
So,
⇒ ∠A + ∠B = 180°
⇒ 20° + ∠B = 180°
⇒ ∠B = 180° – 20°
⇒ ∠B = 160°
So,
⠀
So, If ∠B = 160°, then So, also ∠D = 160°.
Therefore,