Solution - Linear equations with one unknown

Rearrange:

Rearrange the equation by subtracting what is to the right of the equal sign from both sides of the equation :

                     21-r-(-87+2*r)=0 

Step by step solution :

Step  1  :

Pulling out like terms :

 1.1     Pull out like factors :

   108 - 3r  =   -3 • (r - 36) 

Equation at the end of step  1  :

Step  2  :

Equations which are never true :

 2.1      Solve :    -3   =  0

This equation has no solution.
A a non-zero constant never equals zero.

Solving a Single Variable Equation :

 2.2      Solve  :    r-36 = 0 

 Add  36  to both sides of the equation : 
                      r = 36

One solution was found :