Simplify by combining like terms 2rs 7r6s 9rs6 9rs6 7rs
     Simplify by combining like terms. (2rs - 7r^6s - 9rs^6) - (9rs^6 - 7rs + 2 r^6s) 
  
  Solution
Given that
(2rs - 7r6s - 9rs6) - (9rs6 - 7rs + 2r6s) = 2rs - 7r6s - 9rs6 - 9rs6 + 7rs - 2r6s
= 9rs - 9r6s - 18rs6
Therefore ,
(2rs - 7r6s - 9rs6) - (9rs6 - 7rs + 2r6s) = 9rs - 9r6s - 18rs6

