The equations are

The second equation is

Division property of equality: If a = b then a / c = b / c, c ≠ 0.

                           (Divide each side by -6).

                                  (Cancel common terms)

                                          (Divide: )

Substitute 5 for y in equation (1).

                             (Multiply: )

              (Add 15 to each side).

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

                                    (Add: )

Division property of equality: If a = b then a / c = b / c, c ≠ 0.

                              (Divide each side by 3).

                                              (Cancel; common terms)

                                                    (Simplify)

Substitute 7 for x in equation (3).

                           (Multiply: )

          (Add 14 to each side).

                          (Additive inverse property: 14 - 14 = 0)

                                 (Add: )

                            (Divide each side by 5).

                                                 (Simplify)

The solution is