Solve the system of linear equations by substitution. Check your solution. y = x + 2
y = 3x - 4

1. X+2=3x-4
6=2x
x= 3

2. y= 8-x
8-x = 3x+4
4= 4x
X= 1

3. -2x +3(2x+7)=9
-2x + 6x + 21 = 9
4x = -12
x= -3

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.