CEMC Fermat, 2006

Algebra Difficulty 2.0 Junior Find the answer Canada

If the system of equations $px + qy = 8$ , $3x - qy = 38$ has the solution $(x, y) = (2, -4)$ , then $p$ is equal to

(A) $-12$ (B) $20$ (C) $8$ (D) $40$ (E) $21.5$

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