# Thread: Simultaneous Equation Help

1. ## Simultaneous Equation Help

Hello,

What is the value of x that satisfies the following simultaneous equation:

x - y = - 2

5x + 8y = - 23

I have never been excellent at maths. So this might be the simplest simultaneous equation for you but for me I have no clue. I did do some prior research (again might sound like a dummy) and here's what I got on how to solve it:

5x + 8(x+-2) = -23
5x + 8x+-16 = -23
13 + -16 = - 23
13x + 16 = -23
5x = - 23

Please help!

2. ## Re: Simultaneous Equation Help

Originally Posted by Samuel554
Hello,

The problem is to find the value of X:

x - y = - 25x + 8y = - 23
Are you saying you have the two equations
x - y = -23
and
-25x + 8y = -23

Your work indicates something else. Can you please rewrite your question? This makes no sense.

-Dan

3. ## Re: Simultaneous Equation Help

My working was from another site, I don't think I was on the right track so if it's wrong just ignore it :P
I updated the OP, my mistake I forgot to space it out. And yes it's two equations. I included the actual question if it helps. Thanks!

4. ## Re: Simultaneous Equation Help

x - y = - 2 , y = x+2

5x + 8y = - 23

So, 5x + 8(x+2) = -23
5x + 8x +16 = -23
13x = - 39
x= -3

5. ## Re: Simultaneous Equation Help

Another way to do this problem is to multiply the first equation by 8 to get 8x- 8y= -16. The reason for doing that is to get "-8y" which will cancel the "+8y" in the second. Adding the equation 8x- 8y= 16 to 5x+ 8y= -23 gives (8x+ 5x)+ (-8y+ 8y)= -16- 23 or 13x= -39. Now divide both sides by 13 to get x= -3.

Once you have x= -3, the equation x- y= -2 becomes -3- y= -2 or, adding 3 to both sides, -y= 1.