Question 853048
The solution to the two equations that you chose are not -4 and 8  but X = -4/13,   Y = 32/13
why do you think that -4 and 8 would be the solutions?
 5X-Y=-4 
5*4-8=a 
-20-8=-28
 5X-Y=-28 

6X+4Y=8
and 6(-4)+4*8=b. 
  -24+32=8
6X+4Y=8
which is the original equation you had
6X+4Y=8,
5X-Y=-28 
now the solution is x=-4 and y=8
(-4, 8)