Пошаговое объяснение:

1)( 2,5*43,2)-0,4=2.5*43,2=108

108-0.4=107.6

2)13.8*7.8-2.2=13.8*7.8=21.6

21.6-2.2=19.4

3)37*0.5*0.4=7

4)39.8*7.9-39.7*7.9=39.8*7.9=314.42

39.7*7.9=313.63

314.42-313.63=0.79