51.5-8.56-1.44=51.5-(8.56+1.44)=51.5-10=41.5
21*102-21*2=21*(102-2)=21*100=2100
25*125*32=25*4*125*8=100*1000=100000
7.91*3+3*2.09=3*(7.91+2.09)=3*10=30
45*98+45*2=45*(98+2)=45*100=4500