-9x+12y=18



        x-2y=3



Here are the Steps using Substition method

1. In either equation, solve for one variable in terms of the other.



   x - 2y = 3

        x = 2y + 3 

2. Substitute for that variable in the other equation. Solve.



       -9x + 12y = 18,  x = 2y + 3 

      -9(2y + 3) + 12y = 18

      -18y - 27 + 12y = 18

              -6y = 45

                y = -45/6

                  = -15/2

3. Substitute the result from step 2 in either equation. Solve for the other variable.





         x - 2y = 3  , y = -15/2



         x - 2(-15/2) = 3

            x - (-15) = 3

               x + 15 = 3

                    x = -12





4. Check the solution in both original equations.

     

         x - 2y = 3, x = -12 and y = -15/2

  

         -12 - 2(-15/2) = 3

               -12 + 15 = 3

                      3 = 3  ------> true





                  -9x + 12y = 18, x = -12 and y = -15/2

        -9(-12) + 12(-15/2) = 18

                 108  -  90 = 18

                         18 = 18  ----> True





Therefore, the solution is x = -12 and y = -15/2









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