3) 2,929*8,356+2,929*1,644=24,474+4,815=29,289

2,929*(8,356+1,644)=2,929*10=29,29

4) 47,612*3,21-47,512*3,21=152,834-152,513=0,32

(47,612-47,512)*3,21=0,1*3,21=0,321