An Equation That Defines Y as a Function of X $$x - 2 y = 18$$

An equation that defines y as a function of x is given. Rewrite the equation using function notation f(x) .
- $$x - 2 y = 18$$

A) $f ( x ) = \frac { 1 } { 2 } x - 9$
B) $f ( x ) = - \frac { 1 } { 2 } x + 9$
C) $f ( x ) = \frac { 1 } { 2 } x - 18$
D) $f ( x ) = - x + 9$