3,9*5,48+3,9*5,42 решите по действиям

3,9*5,48+3,9*5,42=3,9*(5,48+5,42)=3,9*10,9=42,51--------------------------------------------------------

1)3,9*5,48=21,372;2)3,9*5,42=21,138;3)21,372+21,138=42,51.