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This is shaping the back of the sweater at the neck and working one shoulder at a time.
Next row: K15 (16-16-17-18-19) (knit the number of sts for your size, ending at the neck edge).
Turn. Turn as you would at the end of a row. Now the purl side is facing you.
Leave rem sts on a spare needle. Ignore these sts for now and work on the right shoulder only.
Next row: P2tog. Purl to end of row. This decrease is at the neck edge
Next row: Cast off 6 (6-6-7-7-8) sts. This is shaping the shoulder.
Knit to last 2 sts. K2tog. Again, a dec at the neck edge.
Next row: P2tog. Purl to end of row. A dec at the neck edge. Purl to the end of the row and
Cast off rem 6 (7-7-7-8-8) sts. This shapes the shoulder and binds off the last of the sts.
Now you're going to slip the center neck sts to a holder and work on the left shoulder. I thing that if you follow the directions step by step you should be fine.