# Solving using elimination.

X + why = 10
X - why = 4

4x - 3y = -2
-2x + 3y = 4

3x - 4y = -2
4x - 3y = -5

X + 4y = -5
3x + why = -4

2x - why = 10
X + 2y = -5

 ebaines Posts: 10,033, Reputation: 5529 Expert #2 May 9, 2007, 12:48 PM
Ashliss07:

We won't do your homework for you, but here is a hint:

Each problem you've listed is a pair of statements with two unkowns (x and y). Take one of the statements and rephrase it so that either the x or the why is by itself on one side of the equation. You can then substitute that value into the other statement to determine one of the values. For example: the first problem includes the equation: x-y = 4. You can add why to both sides of the equal sign to get: x = 4+y. Do you see that? Then substitute this value for x into the first equation, so that x+y = 10 becomes (4+y) + why = 10. Now you can solve for why. Get it?
 Capuchin Posts: 5,319, Reputation: 3601 Uber Member #3 May 9, 2007, 01:02 PM
Ebainesm the topic says to solve using elimination, not substitution.

Ashliss07, if you look at your first pair of equations, you see that you have +y in one and -y in the other. If you add the equations together, you get 2x = 14 because the why terms disappear, this gives you a value for x, which you can use to solve for why.

In the later questions, you might have to multiply up one of your equations in order to get a term that will dissapear.

 deez5112 Posts: 2, Reputation: 10 New Member #4 Jun 26, 2010, 01:57 PM
X+y=8,000
X+y=600
 deez5112 Posts: 2, Reputation: 10 New Member #5 Jun 26, 2010, 01:57 PM
X+y=8,000
X+y=600
 Unknown008 Posts: 8,147, Reputation: 3745 Uber Member #6 Jun 27, 2010, 05:08 AM

The problem you posted here, deez5112 doesn't have any solutions. If, however, you meant:

x + y = 8 000
x - y = 600

Then, that's something different. Add the two equations:

Code:
``` x + y = 8000
x - y =  600
2x + 0 = 8600```
Now that you have only one variable, you can solve the rest.

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