You have to loose nine thousand feet - therefore three times nine equals 27 miles. Groundspeed 400 kts, ROD required equals 2000 fpm or so. Apparently this is OK unless you are flying an A330, which requires the four times table.
Unless of couse you have an FMS when your tap in your request and it does the rest (or heaven forbid, you use V/S and use the BOD arc on the ND.
Flying jets etc.. is not rocket science (you might say it's jet science). They are designed to be flown by plonkers (and there are many of them out there, myself included) on bad night.
PS: If you then have to loose speed, more distance has to be added