Solution - Simplification or other simple results

Reformatting the input :

Changes made to your input should not affect the solution:

 (1): "a6"   was replaced by   "a^6". 

Step  1  :

Equation at the end of step  1  :

  0 -  ((2•3a6) • a)
 Step  2  :

Final result :

  ( -2•3a7)