Problem understanding instructions

I am knitting a shawl and I can’t understand this one part of the instructions. It says "P1; *P3, pass first of 3 sts just purled over 2 sts; rep from * across: 75 st. The row before that I understand you K1; *YO, K2; rep from * across 112 st. I have almost frayed the yarn trying to figure this out It sounds like decreasing but I can’t find out how to do it. Please help me with this. Thank you

It’s a decorative st, but will dec to get the stitch count back to what it was from the YO increase on the previous row.

P3 sts, they’re on you’re right needle, then lift the 1st one of the 3 sts over the other 2. Like you’d do a bind off.