428-299zen怎样简便运算

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428-299zen怎样简便运算

428-299
=428-(300-1)
=428-300+1
=128+1
=129

428 - 299 = (400 - 200) + (28 - 99) = 200 -71 = 129.

128+(300-299)=128+1=129

428-299
=428-(300-1)
=428-300+1
=128+1
=129