They think I know what I'm doing!

Having some problems with this pattern as far as the decrease goes.

**dec 1 st at armhole edge on next and foil 2 alt rows at the same
time dec 1 st at front slope edge as set on every 3rd row from
previous dec. 29 sts.
Dec 1 st at front slope edge only on every foll 3rd row from previous
dec until 22 sts rem.
Cont straight until work meas 8Y2 in (22

So do I count the purl rows (alt) when determining every following 3rd row or does this just mean the pattern rows ?

An ‘alt row’ means every other row, patterned or plain. Start by decreasing on the next row then work a row plain, dec on next row, plain row and dec on next row. That’s at the [I]armhole edge only[/I]. At the neck edge you begin the decs on the 3rd row which would be a purl row. Then work 2 rows and dec on the 3rd one again, only it would be at the end of a knit row.

You’re doing decs at both the armhole and neck edges, but at different rates - every other row for the armhole, and every 3rd row at the neck.