

The equations are
\ Equation (1)
                                   Equation (1)
 Equation (2)
                                 Equation (2)
Since the coefficients of the m-terms are same, you can eliminate these terms by subtracting the equations. Subtract the equations to eliminate variable m.
\Write the equations in column form and subtract the corresponding columns.
\
Apply division property of equality: If a = b then  
 
 (Divide each side by 2)
                               (Divide each side by 2)
 (Cancel commmen terms) \ \
                                    (Cancel commmen terms) \ \
 (Divide:
                                    (Divide:  )
)
Now Substitute 4 for n in either equation to find the value of m.
\ (Equation 1)
                       (Equation 1)
 (Replace n = 4)
                    (Replace n = 4)
 (Multiply:
                       (Multiply:  )
)
\
Apply addition proparty of equality: If a = b then 
 (Add 20 to each side)
       (Add 20 to each side)
 (Additive inverse property:
                               (Additive inverse property:  )
)   
 (Add:
                                 (Add:  )
)
 (Divide each side by 2)
                            (Divide each side by 2)
 (Cancel commmen terms)
                                 (Cancel commmen terms)
 (Divide:
                                      (Divide:  )
)
The solution is 
The solution is  .
.