Substitution:

Given equations are,

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

          ------(2)

The second equation is already solved for c,

so,  substitute for y in the first equation.

                  (First equation)

         (Substitute  )

Apply distributive property: .

             (Multiply: )

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

   (Subtract 2 from each side)

         (Apply additive inverse property: )

                (Apply additive identity property: )

                      (Subtract: )

      (Subtract 3d from each side)

   (Apply commutative property: )

             (Apply additive inverse property: )

                   (Apply additive identity property: )

                                        (Subtract: )

Substitute for d in either equation to find c.

                           (Second equation)

                        (Substitute  )

                              (Subtract: )

The solution is .

Check the solution:

To check, Substitute   and in either equation.

                             (Second equation)

                       (Substitute  and )

                             (Subtract: )

The solution  is true.

If the system have only one solution, such as .

If the system have only one solution, such as.