Alternate solution is that you begin and end with a k or p outside the pattern (rib or dec) for a selvage edge for the seam up the back.
What is the rib pattern that you didn't have trouble with 53 stitches... 53 is prime so no size repeated rib would end evenly. :think:
There must be one selvage stitch at the start and end of each row for the seam. leaving 51 sts for the repeated pattern. 53 is a multiple of 3.
So for decrease row: k1 (k1, k2 tog) repeat across and then k last stitch.
Or K1 (k2 tog, k1) across and k1 last stitch.
But for the next decrease you have 36 stitches or 12 repeats of (k1, k2 tog) which leave 24 on needle.
then 16 sts after third decrease
Fourth decrease row again you would need to k1 at beginning or end of 5 repeats of (k1, k2 tog) leaving 11 sts on needle.
But the pattern expects you to stop decreases at 12 stitches? :wall: