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Question
In a trapezium ABCD, side AB is parallel to side DC. If ∠A = x° and ∠D = (3x – 20)°; find the value of x.
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Solution
∵ AB || DC and BC is transversal
∴ ∠A and ∠B are Co-interior angles with their sum = 180°
i.e. ∠A + ∠D = 180°

⇒ x° + (3x – 20)° = 180°
⇒ x° + 3x° – 20° = 180°
⇒ 4x° = 180° + 20°
x° = `200/4` = 50°
∴ Value of x = 50°
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