2x + y = 18

4x - y = 12

Solution:

x = 5, y = 8

Add both equations together 6x = 30 and so x = 5 and therefore y = 8

:-

Method 1

2x. + 4x - 12 = 18

6x = 30

x. = 5

10 + y = 18

y = 8

Method 2

4x + 2y = 36

4x - y = 12____subtract

3y = 24

y = 8

4x. = 20

x. = 5

2x + y = 18 and 4x - y = 12   so

2x + (4x - 12) = 18

6x = 30, so x = 5

y = 18 - 2x = 18 - 2*5 = 8

2x + y = 18 

4x - y = 12  

Solution:

x = 5, y = 8

Just add the two equations, and you get

6x = 30.  So x = 5

Now replace x with 5 in either equation to find y,

and you're done