(475+666)+525=666+(475+525)运用了加法结合律和交换律.
285+374=374+285
86+75+25=86+(75+25)
48+27+52+73=(48+52)+(27+73)
27+45+73=27+73+45
85+313
42+87+58
(73+64)+37
56+78+44
(206+189)+294
(73+37)+64
189+(206+294)
313+85
87+(42+58)
78+(56+44)