Question 696644
x + 2y = 9 ----->  -x - 2y = -9   {multiplied top equation by -1}
x - y = 3  ----->   x - y = 3   {bottom equation stays the same}


-3y = -6   {added the two equations together}
y = 2   {divided each side by -3}
<br>For more help from me, visit: <a href = "http://www.algebrahouse.com/" target = "_blank">www.algebrahouse.com</a><br><br><br>