math

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Elimination Method....I am not understanding this method either and need some help here is what I am working on:

1)
x+8y=33
-x+4y=3

2)
5x+5y=-7
7x-2y=13

3)
0.3x-0.2y=4
0.5x+0.3y=-7/17

• math -

in this method you are trying to get the coefficients of one set of variables to be either the same or opposites.
If you get them to be the same, you would then subtract the two equations from each other, and if they are opposite, you would add the equations.

I will do the second
looking at the y's, I notice it would be nice if they were both 10, so
multiply the first by 2 ----> 10x + 10y = -14
multiply the second by 5 --> 35x - 10y = 65
add them ----> 45x = 51
x = 51/45 = 17/15
sub that back into the "easier" original equations
I pick #2 , in this case it doesn't make much difference
7(17/15) - 2y = 13
-2y = 13 - 119/15
y = -38/15

do the others the same way

• math -

I am still confused on number one because it starts with the same variable so I don't really know where to start can you help....?

• math -

I am also confused as to how to work the fraction part of number 3 can you help?