This is actually a bit of a trick question since the two equations are equivalent.
If you solve y+4=-2x for y you'll get y=-2x-4 which is the same as the first equation mentioned in the question.
In a case like this, where you have more variables than equations (there are 2 variables- x and y, but only equation of y=-2x-4) there will actually be infinitely many solutions. You can keep plugging in infinitely many values for x and keep getting outputs for y.
Notice that y=-2x-4 is just the equation of a straight line in the form of y=mx+b, where the line is continuous for all real numbers (so for all x). That's why this this isn't really a "system". The two equations in the question equal each other, hence there is only one net equation, In that net equation, you can have any value for x (or y) plugged in and a different solution can be found each time.
