# Confusion on a subtraction problem

$$\frac{x}{x^2-9} - \frac{1}{2x-6}$$

When I first worked this problem I found the answer to be:
$$\frac{1}{2x-6}$$

However, in my English class we had this Vietnamese substitute who took my worksheet and did the problems on it in his head and pointed at the answer I wrote for this problem and walked away. He came back and worked it out in front of me and he got the answer:
$$\frac{1}{2x+6}$$

dextercioby
$$\frac{x}{(x-3)(x+3)}-\frac{1}{2(x-3)}$$