Answer:
y=−x+2y=4x+7  NO
y=−x+2        YES
y=4x+7 Â Â Â Â Â Â
Multiply the first equation by 4, obtaining: Â Â Â Â Â Â Â 4y = -4x + 8
Add the 2nd equation to this result:              y = 4x  + 7
                                      --------------------
                                        5y = 15, and y = 3
Then, using the first equation, determine x:
y = 3 = -x + 2
   1 = -x, so x = -1
The solution is (-1, 3)