The equations are

 Since the coefficients of the x-terms,+1 and -1,are additive inverses,

you can eliminate these terms by adding the equations. .

add the equations to eliminate variable x.

                 (Write the equations in column form and add)

                           (Divide each side by 3)

                                (Cancel common terms)

                                     (Divide: )

Now Substitute 6 for y  in either equation to find the value of x.

   (Equation 1)

                          (Multiply:  )                           

         (subtract 12 from each side)

                    (Additive inverse property: )

                           (Additive indentity property: )

                                       (Subtract:  )

The solution is .

The solution is .