Shaping armholes on a sweater

Hi knitters ! :waving: I’ve got a question for you.

I’m making a sweater and I’m to the shaping the armholes part of the back of the sweater. It is a bottom-up pattern. I have 46 sts on the needle. So, the pattern says to cast off 3 sts at the beginning of the next 2 rows. I did that.
Then, it says to decrease 1 st at each end of next 3 rows, then on the following alternate row. I should then have 32 sts.

Now, my question: don’t you usually do decreases on the right side of the sweater only? I pretty much only knit top down seamless sweaters, but I don’t remember do decreasing on the purl side (ws).

You can just purl 2 together. Decreases can be done on either side, depending on how often you need to do them.