The equations are

                   Equation (1)

                  Equation (2)

Multiply the equation (2) by 2.

                 Equation (3)

Add equation (3) and Equation (1).

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

                            (Divide each side by 7)

                                 (Cancel common terms) \ \

                                      (Divide: )

Substitute 3 for p in equation (1).

                         (Multiply: )

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

             (Add 9 to each side)

Apply commutative property of addition: a + b = b + a.

                            (Apply Additive inverse property: 9 + 9 = 0)

                                      (Add: 3 + 9 = 6)

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

                                (Divide each side by 6)

                                       (Cancel common terms) \ \

The solution is .