Math Help - Solving for x and y, etc...

Ok I am confused with these problems:

Solving for X and Y using substitution:

1. 2x+y=4
3x-y=6

2. 3x+15y=3
2x-5y=-28

3. 4x-5y=0
8x-10y+15

Solving for X and Y using linear addition:

4.5x-7y=2
3x=4y

5.10x+10y=40-5x
9x+2y=32-6y

6. 2x=8y+24
3x+5y=2

Originally Posted by peachgal

Ok I am confused with these problems:

Solving for X and Y using substitution:

1. 2x+y=4
3x-y=6

You have two equations and two unknowns. Start with the first equation: 2x+y=4. Solve for y.

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

Now take this and plug in "4-2x" for "y" in the second equation.

3x-y=6
3x-(4-2x)=6
3x-4+2x=6
5x-4=6
5x=10
x=2

Now that we have found x, plug "2" in for "x" in either the first or second equation to find y.

2x+y=4
2(2)+y=4
4+y=4
y=0

So the final answer is x=0, y=2. If you plug in these numbers to both equations you can verify they are correct.