The equations are .

      Equation (1)

          Equation (2)

Since the coefficient of x is same in both equations, either equation can be used for solution. Solve the second equation for x.

Apply addition property of equality: If a = b then a + b = b + a.

               (Add y to each side)

                          (Apply additive inverse property: )

Substitute in equation (1).

                       (Add: )

Apply subtraction property of equality: If a = b then a b = b a.

Apply commutative property of addition: .

                     (Apply additive inverse property: )

                           (Apply additive identity property: )

                                   (Subtract: )

Apply division property of equality: If a = b then .

                              (Divide each side by 4)

                                     (Cancel common terms)

Substitute in equation .

                                    (Add: 8 + 1 = 9)

The solution is .