21x19+21x8o-99=几用简便方法计算

2025-04-14 23:53:36
推荐回答(2个)
回答1:

21x19+21x80-99
=21x(19+80)-99
=21x99-99
=99x(21-1)
=99x20
=1980

回答2:

=21×(19+80)-99
=21×99-99
=(21-1)×99
=20×99
=1980