Data Sufficiency

Any correct explanations would be awesome

Question1:
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BAC = 180-3x
DBC = 180-4x
Therefore ABD = x.

Angle ABD = Angle BAD. therefore the sides have to be equal

1) according to statement1, AD=6, therefore BD = 6, which implies BC =6 (BDC = BCD).
2) X=36 doesn't give us anything.

Therefore 1 alone is sufficient. Answer is: A

Question2:
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Statement 1 gives us slop. Using y=mx+c (assuming c =0) we can easily conclude that the line passes through quandrants 2 and 4. Therefore 1 alone is sufficient.

Statement 2 just gives us y intercept. We need slope. therefore it is not sufficient.

Answer is: A.

Thank you for the response.
But with question 2 :
How do u assume c = 0???

Thank you for the response.
But with question 2 :
How do u assume c = 0???