Question

my answer is A.30, but in the Ans keys it is D.15, which one is correct? ​

Answer 1

Answer:

angle ABC = ACB (OPOSITE ANGLES OF EQUAL SIDE ARE EQUAL )

AND

ABC + BAC + BAC = 180° ( SUM OF ALL ANGLES OF TRIANGLE = 180 °)

BAC +BCA + CAB = 180°

40 ° + 2 BCA =180° ( ABC = ACB)

2 BCA = 180° -40°

2BCA = 140°

BCA = 140°/2

BCA = 70°

ABC = 70° (ABC=BCA)

ABC+CBD+DBF = 180° ( SUM OF ANGLES ON SALE LINE = 180°)

70° + CBD + DBF = 180° (ABC = 70°)

70° + 2CBD = 180° ( CBD = DBF , GIVEN)

2 CBD = 180°-70°

2 CBD = 110 °

CBD = 110°/2

CBD = 55°

ACB - DBF = 70° - 55°

= 15

SO REAL ANSWER = 15

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