Áp dụng t/c dtsbn:
\(\dfrac{x}{-5}=\dfrac{y}{-6}=\dfrac{3x}{-15}=\dfrac{2y}{-12}=\dfrac{3x+2y}{-15-12}=\dfrac{51}{-27}=-\dfrac{17}{9}\)
\(\Rightarrow\left\{{}\begin{matrix}x=\left(-\dfrac{17}{9}\right).\left(-5\right)=\dfrac{85}{9}\\y=\left(-\dfrac{17}{9}\right).\left(-6\right)=\dfrac{34}{3}\end{matrix}\right.\)