Algebra
posted by Jonnie .
I need help with this problem
0.3x0.2y=4
0.5x+0.5y=45/23
3x2y=40
5x+5y=450/230
6x47=80
15x15y=1350/230
x=5
is this right I need your help.

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!)