there is no solution. if you are using the two equations to solve for y and x.
you can plug one equations into the other.
substituting one of the y gives...
3(x+4)=3(x-4)
÷ both sides by 3 gives x+4=x-4
get x on one side and numbers on the other
x-x =4+4
and x-x will give you a 0 for the left side
therefore 0 = 4+4.. not true.