[SOLVED] Solving sim equations.

I need some real help with this please guys, ok so here's the example given to me from tutor:

Example 2*x* + *y* = 1, *x* + 3*y* = -7

__Method 1 - add/subtract__

__ __

2*x* + *y* = 1

*x* - 3*y* = 11

You can add or subtract. Adding will enable you to focus on *x*, subtracting will focus on *y*.

Perhaps the easiest is to add. BUT first of all you must scale the first expression by 3 to enable the *y*’s to match, giving the zero count for *y*, you require.

So 6*x* + 3*y* = 3 (Note each part has been x 3)

*x* - 3*y* = 11

Adding 7*x* = 14 (Note the zero count for y - this is what you *x* = 2 want to happen)

Substituting back into one of the previous expressions -

2(2) + *y* = 1, 4 + *y* = 1, *y* = -3

__ANSWER __*x* = 2, *y* = -3

My first problem is, from the example equations, how can it be re-arranged and make 11?!

I'm confused with this topic, thanks

ADY