Find the Specified Domain $( f - g ) ( x )$

Multiple Choice

Find the specified domain.
-Find the domain of $( f - g ) ( x )$ when $f ( x ) = 6 x - 9$ and $g ( x ) = 6 x - 5$

A) $( - 9,6 )$
B) $( - \infty , \infty )$
C) $( - 6,9 )$
D) $( - 6 , \infty )$