The equations are

                       Equation (1)

                       Equation (2)

Since the coefficients of the s-terms are same, you can eliminate these terms by subtracting the equations. Subtract the equations to eliminate variable s.

Write the equations in column form and subtract the corresponding columns.

Now Substitute –5 for r in either equation to find the value of s.

                                     (Equation 1)

                              (Replace r  = –5)

                                  (Multiply: )

Apply addition proparty of equality: If a = b then

                  (Add 15 to each side)

                  (Cancel commmen terms)

                                              (Additive inverse property: ) 

                                           (Add: )

Apply division property of equality: If a = b then

                                       (Divide each side by –5)

                                              (Cancel commen terms)

                                                      (Divide: )

The solution is          

The solution is .