Solve the following system of equations with the substitution method: \left\{\begin{array}{l} 12 x-3 y=3 \\ y \quad 4 x-1 \end{array}\right. Solve the given linear system of equations: \left\{\begin{array}{l} 9 x-6 y=-15 \\ -6 x+4 y=10 \end{array}\right.

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