Pattern Question

I am making a sleeveless cardigan with one button (pattern titled Aon). The pattern has me work in 2x2 ribbing for 1.5 inches. Then it has be change to larger needles and states the following:

p the next row, decreasing 28 sts across - 82 sts.

I will be starting this row with 110 sts. How do I decrease 28 sts across? I plan to decrease by purling 2 sts together but I don’t know where to decrease. How do I determine where the decrease should occur?

Thanks

Here you go! This should help.
http://www.thedietdiary.com/knittingfiend/tools/EvenlySpace.html