plz help with system

as said, start by isolating y: 
5x + y = 31
        y = 31 - 5x

then substituting that into the second equation: 
3x + 4y = -37
3x + 4(31 - 5x) = -37
3x + 124 - 20x = -37
        124 - 17x = -37
               - 17x = -161
                     x = $9\frac{8}{17}$

now you can substitute the x value back into the first equation to find y: 
y = 31 - 5x 
   = 31 - 5( $9\frac{8}{17}$ )
   = 31 - $47\frac{6}{17}$
   = $-16\frac{6}{17}$

so your answer would be $(9\frac{8}{17}, -16\frac{6}{17})$. 

hope this helps and tell me if I did anything wrong :)