The equations are

                    Equation (1)

                      Equation (2)

Multiply the equation (2) by 2

                    Equation (3) 

Subtract the equation (3) and equation (1) to eliminate the m variable

          (Subtract the corresponding columns)

Substitute in equation (2).

                 (Multiply: )

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

(Add 20 to each side)

           (Apply Additive inverse property: )

                 (Apply Additive identity property: )

                         (Add: )

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

                           (Divide each side by 5)

                         (Cancel common terms)

                              (Divide: )

The solution is .

The solution is .