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“after 9 rows of K2 P2 rib, the 10th line instruction line says *Inc once in each of next 2 sts, rib 3, rep from * to last 3 sts, inc once in each of next 2 sts, rib 1.”
It depends on the increase you’re gong to do but for a knit front and back increase (kfb) and assuming you’re starting with a K2 this would be *Kfb, Kfb, P2, K1 then the first repeat is Kfb, Pfb, P1, K2 and so on to the last 3sts. The final increase depends on how many sts you have and whether they are knit or purl sts.
The easiest way to do this is to work the 2 increases and then work 3 sts as either knits or purls, depending on the columns of ribbing you’ve already knit. Don’t worry about writing it out. It’s a way of reading your knitting.