Please help

My pattern says to
Cast off 3 at at beg of next row (31 sts)
Dec 1 st at beg of next and foll 2 alt rows (28sts).
Also later on to shape front slope
Dec 1st at end of next row and at this same edge on following 8 rows (19 sts)
The front is longer than the back. Can someone please break this down.
Thanks

All patterns are different. Can you tell us the name of the pattern and give a link if possible? (Don’t post the whole pattern or a picture of it please)

Welcome!
It really is enormously helpful to have a link to the pattern, a pattern name and a photo.
The first directions are to cast off 3sts at the beginning of row 1 and then decrease one st at the beg of rows 2,4,and 6.
The second directions which occur later mean to dec one st at the end of row 1 and at the same edge on rows 2,3,4,5,6,7,8, and 9.