The equations are

The second equation is .

Apply division property of equality: if a = b, then.

                 (Divide each side by negative 6)

                         (Cancel common terms)

                                  (Divide: )

Substitute 5 for y in equation (1).

                             (Multiply: )

Apply addition property of equality: if a = b, then a + c = b + c.

            (Add 15 to each side)

                              (Apply Additive inverse property: - 15 + 15 = 0)

                                     (Add: )

Apply division property of equality: if a = b, then.

                               (Divide each side by 3)

                                    (Cancel common terms)

                                         (Divide: )

Substitute 7 for x in equation (3).

                            (Multiply:)

Apply addition property of equality: if a = b, then a + c = b + c.

          (Add 14 to each side)

                            (Apply Additive inverse property: )

                                    (Add: )

Apply division property of equality: if a = b, then.

                              (Divide each side by 5)

                                   (Cancel common terms)

                                        (Divide: )

The solution is .