Decreasing at neck edge

when it says to decrease by neck do you decrease going to the left only or going right also.

Both ways, sometimes you may have to decrease on a WS row.

I work mirror image decreases on each side of the neck.

I haven’t come across a pattern yet that the neck decreases weren’t always worked from the RIGHT SIDE facing. But, just in case a mirror image decrease (whether for armholes or necklines) needed a decrease from the WRONG SIDE facing, you can still execute a perfect mirror image decrease.