Question 34053
x+y=6
x-y=12<br>

solve the second eqution for x
x=12+y<br>

substitute 12+y in for x in the first equation
(12+y)+ y = 6
12+2y=6
2y=-6
y=3<br>

plug 3 into the equation that sloved for x
x=12+y
x=12+3
x=18