Answer :
[tex]\left\{\begin{array}{ccc}-5x-6y=-9&/\cdot2\\3x+4y=25&/\cdot3\end{array}\right\\+\left\{\begin{array}{ccc}-10x-12y=-18\\9x+12y=75\end{array}\right\\------------\\.\ \ \ \ \ \ \ -x=57\\.\ \ \ \ \ \ \ \ \ x=-57\\\\3\cdot(-57)+4y=25\\-171+4y=25\\4y=25+171\\4y=196\ \ \ \ /:4\\y=49\\\\Solution:x=-57;\ y=49.[/tex]
