Given the expression :
Note : we have taken 12 as common from 12x²-108, the result will be 12 (x²- 9 )
and 36 as a common from 36x-108, the result will be 36 ( x - 3 )
(x²- 9 ) = ( x - 3) ( x + 3) [ the difference between two complete squares ]
then we have simplified the rational expression
so, the answer is option c) (x+3)/3