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addition and substitution methods

mathbites13

New member
Joined
Dec 14, 2009
Messages
1
PLEASE HELP ME SOLVE THESE

USE THE ADDITION METHOD TO SOLVE THIS
18X + .27Y = .09
.06X - .54Y = -.04

USE THE SUBSTITUTION METHOD TO SOLVE THIS
X + 6Y =2
5X - 20Y = 5

I NEED THIS VERY SOON PLEASE PLEASE SOMEONE HELP I HAVE SPENT HOURS ON THIS AND IM GETTING NO WHERE DUE TOMORROW
 

wjm11

Senior Member
Joined
Nov 13, 2004
Messages
1,417
USE THE ADDITION METHOD TO SOLVE THIS
18X + .27Y = .09
.06X - .54Y = -.04
I will assume that the "18" is supposed to be ".18". First, multiply both equations by 100 to get rid of all the decimals:

100[.18X + .27Y] = 100[.09]
18x + 27y = 9
100[.06X - .54Y] = 100[-.04]
6x - 54y = -4

So now it looks like this:
18x + 27y = 9
6x - 54y = -4

Multiply the top equation by 2 and add the two equations together. Y will be gone, and you'll be left with one equation with x in it.
Solve for x, then solve for y by plugging x back into one of the equations.

USE THE SUBSTITUTION METHOD TO SOLVE THIS
X + 6Y =2
5X - 20Y = 5
Rearrange the top equation to solve for either x or y. To solve for x it would be
x = 2 - 6y

Then substitute that in place of x in the second equation:
5(2 - 6y) = 5

You should be able to handle it from here.

Next time, please show some work.
 
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