### Instruction: Find the phase shift of the graph of $y = \sin (3x - \pi).$.### Response: I recall that the phase shift of a sine function is the horizontal distance that the graph is shifted from the standard sine curve $y = \sin x.$
I also remember that the phase shift depends on the coefficient and the constant term in the argument of the sine function.
Specifically, if the argument has the form $ax + b,$ then the phase shift is $-b/a.$
In this problem, the argument is $3x - \pi,$ so I can identify $a = 3$ and $b = -\pi.$
Therefore, the phase shift is $-\frac{-\pi}{3} = \frac{\pi}{3}.$