#### PreAlgebraDummy15

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x+y=5

5x-3y=17

________

-4x-2y=-12

thats what I got so far (the bottom equation) if anyone can tell me if it's right and maybe help me with the next step that would be great! Thanks

- Thread starter PreAlgebraDummy15
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x+y=5

5x-3y=17

________

-4x-2y=-12

thats what I got so far (the bottom equation) if anyone can tell me if it's right and maybe help me with the next step that would be great! Thanks

1) x+y=5

2) 5x-3y=17

________

3) -4x+4y=-12

4) -x+y=-3

If you then add 1) & 4) you get

2y = 2

y=1

With no substitution.

For substitution you solve 1) for x

x=5-y

then substitute in 2) to get

5(5-y)-3y=17

Then you solve that for y and substitute in 1) and solve for x.

WHY did you subtract ? Is that the way you were taught? I HOPE NOT!PreAlgebraDummy15 said:

x+y=5

5x-3y=17

________

-4x-2y=-12

thats what I got so far (the bottom equation) if anyone can tell me if it's right and maybe help me with the next step that would be great! Thanks

Multiply 1st equation by 3; now you have:

3x + 3y = 15

5x - 3y = 17

Now add them:

8x = 32 : OK?

IF you were TOLD to use substitution, then this way:

x+y=5 : y = 5 - x

Substitute that in 2nd equation:

5x-3y=17 : 5x - 3(5 - x) = 17 : 5x - 15 + 3x = 17 : 8x = 32 ; OK?

- Joined
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It did thanks. I have another question:

7c+5d=18

c-5d=-2

________

6c=16

__ __

6 6

c=2 4/6= 2 2/3

Is that right so far?

Why is everything always "urgent" with you? It gets old and annoying. FYI- New problems, new posts.PreAlgebraDummy15 said:It did thanks. I have another question:

7c+5d=18

c-5d=-2

________

6c=16

__ __

6 6

c=2 4/6= 2 2/3

Is that right so far?