[tex] \left \{ {{2x+y=11} \atop {2x-4y=-14}} \right. [/tex]
2x+y=11 (subtract 2x from both sides)
y=-2x+11
2x-4y=14
2x-4(-2x+11)=-14 (substitute for y)
2x+8x-44=-14
2x+8x=30 (add 44 to both sides)
10x=30 (divide both sides by 10)
x=3
Now substitute for x:
2x+y=11
2(3)+y=11 (substitute y with 3)
6+y=11 (subtract 6 from both sides)
y=5