[tex]\left\{\begin{array}{ccc}8x=9-5y&(1)\\8x-3y=-31&(2)\end{array}\right\\\\subtitute\ (1)\ to\ (2)\\\\(9-5y)-3y=-31\\9-5y-3y=-31\\9-8y=-31\ \ \ \ |subtract\ 9\ from\ both\ sides\\-8y=-40\ \ \ \ |divide\ both\ sides\ by\ (-8)\\\boxed{y=5}\\\\subtitute\ value\ of\ y\ to\ (1):\\\\8x=9-5\cdot5[/tex]
[tex]8x=9-25\\8x=-16\ \ \ |divide\ both\ sides\ by\ 8\\\boxed{x=-2}\\\\Answer:\boxed{ \left\{\begin{array}{ccc}x=-2\\y=5\end{array}\right}[/tex]