# Thread: Solve for an ordered pair using the substitution method

1. ## Solve for an ordered pair using the substitution method

I'm stuck when looking for the ordered pair via the substitution method for the following equations;
1) 8x-8y= -32
2)9x+84 = y

Thanks for the help...

2. Originally Posted by jay1
I'm stuck when looking for the ordered pair via the substitution method for the following equations;
1) 8x-8y= -32
2)9x+84 = y

Thanks for the help...
$\displaystyle y=9x+84$

and $\displaystyle 8y=8x+32$

Where are you stuck?

3. What is the best way to find the variables?

4. I thought you had to use substitution?

Here are the stages required:

1) Divide my bottom equation by 8
2) Substitute for y, leaving you with a single equation in terms of x
3) Collect like terms
4) Solve for x
5) Resubstitute to solve for y.

Post an attempt if you're still unable to get anywhere.

5. 1. x - y = -4, i.e. x + 4 = y.
2. 9x + 84 = y
∴ x + 4 = 9x + 84, i.e. 8x = -80, hence x = -10.
y = -10 + 4 = -6.
∴ (x, y) = (-10, -6)

6. He's never going to learn if you spoon feed him answers johnny

7. Originally Posted by jgv115
He's never going to learn if you spoon feed him answers johnny
That is his modus operandi...

http://www.mymathforum.com/viewtopic.php?f=13&t=21048

(he changed his handle to "Neo..." for reasons that I'll let him explain)