The equations are

 Since the coefficients of the x-terms,-9 and +9,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 negative 2)

                                (Cancel common terms)

                                     (Divide: )

Now Substitute 7 for y  in either equation to find the value of x.

   (Equation 1)

                    (Multiply:  ) \ \

     (Subtract 28 from each side)

               (Additive inverse property: )

                     (Additive indentity property: )

                             (Subtract:  )

                        (Divide each side by negative 9)

                                   (Cancel common terms)

                                        (Divide: )

The solution is .

The solution is .