Algebra

How do I solve this For (-x)?
(Do I just make -x equal 1 or 2?) I’m suppose to solve the equation by elimination. (Can someone give me steps to solving it and I’ll try to do it and you guys check my work?)
7x-9y=21
-x-18y=-3

asked by Samantha
  1. multiply the 1st equation by -2, then add the result to the 2nd equation
    ... this will eliminate y

    solve the subsequent equation for x

    posted by Scott
  2. I tried doing that but I think I went wrong somewhere because I did

    7x-9y=21
    -x-18y=-3

    -2•7=-14
    -2•9=-18
    -2•21=-42

    14x-18y=-42
    -x-18y=-3

    And got -x-0y=-3
    -x=-45

    ...I know this is wrong, can someone help me

    posted by Samantha
  3. you lost the minus sign on the 14

    you did this ... -2•9=-18
    ... the 9 was negative
    ... to give a positive 18 for cancelling with the -18 in the 2nd equation


    should end up ... -15x = -45

    posted by Scott

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