Need help with shaping Raglan sleeves

I have a king cole cabled sweater pattern and I don’t understand shape raglan armholes, keeping pattern correct , cast off 3sts at beg of next 2 rows. 124 sts. Dec 1 st at each end of next 1 row, then 1 foll 4th row, then on foll 35 alt rows, 50 sts

Hi can you provide the link to the pattern?

I purchased the pattern at a store, there’s a link to pattern but need to purchase.
http://athenbys.com/King-Cole-3964-Knitting-Pattern

Welcome to KH!
Cast off 3 sts at the beg of the next two rows (rows 1 & 2). Dec 1 stitch at each end of row 3, then row 7 and then rows 9.11.13.15.17.19. etc to 50 sts. For the decrease rows, that’s 2 sts decreased per decrease row.
Very good looking sweater.

Thanks for the help