$$\left\{\begin{matrix} \frac{ 3x+9y }{ 5x-6y } = \frac{ 21 }{ 17 } \\ \frac{ 4x-7y }{ 2y+1 } =-2 \end{matrix}\right.$$
$x=-\frac{31}{53}\approx -0.58490566$
$y=-\frac{6}{53}\approx -0.113207547$
