Posted by **Jonnie** on Thursday, April 2, 2009 at 9:19pm.

I need help with this problem

0.3x-0.2y=4

0.5x+0.5y=45/23

3x-2y=40

5x+5y=450/230

6x-47=80

-15x-15y=1350/230

x=5

is this right I need your help.

- Algebra -
**Reiny**, Thursday, April 2, 2009 at 10:45pm
when you multiply 0.5x+0.5y=45/23 by 10 you get

5x + 5y = 450/23

(you don't multiply top and bottom by 10, if you did, you wouldn't have changed the right side at all, only the left side.

And remember, whatever you do to one side, you must do to the other)

I would then divide 5x + 5y = 450/23 by 5 to get

x + y = 90/23 , (notice we could have just doubled the original to get the same result)

now

3x - 2y = 40, and

2x + 2y = 180/23

adding

5x = 40 + 180/23

x = 8 + 36/23

= 220/23

sub that into x+y= 90/23

220/23 + y = 90/23

y = 90/23 - 220/23

= -130/23

( I subbed both of my answers in the original equations and they work!)

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