(2 3\4+0,15-1 8\25) 21\2-13\4+0,04)=(11/4+15/100-33/25) / (21/2-13/4+4/100)=(275/100+15/100-132/100) / (1050/100-325/100+4/100)=(158/100) / (729/100)=158/100*100/729=158/729