Elimination method:

Given equations are,

----------(1)

----------(2)

When the coefficients of a variable and are same,

subtracting the equations will eliminate the variable.

Subtracting (1) and (2) equations will eliminate the variable t.

               (Subtracting (1) and (2) equations)

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

                            (Divide each side by 3)

                                 (Cancel common terms)

                                   (Divide: )

Substitute for r in either equation to find z.

                             (First equation)

                      (Substitute  )

                          (Multiply: )

Apply commutative property of equality:  .

           (Add 18 to each side)

                    (Apply additive inverse property: )

                          (Apply additive identity property: )

                                (Add: )

                   (Multiply each side by negative sign)

                            (Product of two same signs is positive sign)

                                (Product of two different signs is negative sign)

                           (Divide each side by 6)

                                (Cancel common terms)

                                              (Divide: )

Check the solution:

To Check, substitute and  in either equation.

                                (First equation)

                  (Substitute and  )

                           (Multiply: )

                                         (Add: )

The solution  is true.

The solution is .