Solve the following system of equations algebraically.
x + 2y = 18
y = x-3
X=
y =

You plug in the equation of y into x.
X+2(x-3)=18
Gives you the answer of, x = 8
Then you plug in x which is 8 Into the equation of y.
So, y = 8-3
Which gives you
Y = 5
The answer is
X = 8
Y = 5

The first one, i believe, would be correct. all the others have one thing in common, and that's that they have repeating numbers. in the second one, x and y have repeating 6's and 3's, and in the third, x and y have repeating 6's as well. in the last one, there are repeating 3's. the first one has no repeating numbers.