1) 4,45+(5,89+25,55)=(4,45+25,55)+5,89=30+5,89=35,89;
2) 5,17−(4,17+0,12)=(5,17−4,17)−0,12=1−0,12=0,88;
3) (9,871+4,513)−2,513=9,871+(4,513−2,513)=9,871+2=11,871;
4) 2,5⋅7,8⋅0,004=(2,5⋅0,004)⋅7,8=0,01⋅7,8=0,078;
5) 4,2⋅5,4+5,4⋅4,8=5,4⋅(4,2+4,8)=5,4⋅9=48,6;
6) 7,43⋅9,2−5,43⋅9,2=9,2⋅(7,43−5,43)=9,2⋅2=18,4.