### Instruction: Find the phase shift of the graph of $y = \sin (3x - \pi).$.### Response: To find the phase shift of a sine graph, I need to compare it to the basic sine graph of $y = \sin x.$
The phase shift is the horizontal distance that the graph is shifted left or right from the basic sine graph.
I can rewrite the equation of the graph as $y = \sin (3(x - \frac{\pi}{3})).$
This makes it easier to see that the graph is shifted to the right by $\frac{\pi}{3}$ units, since the argument of the sine function is $x - \frac{\pi}{3}.$
Therefore, the phase shift of the graph is $\frac{\pi}{3}.$