1298+789怎么简算

问题描述:

1298+789怎么简算

1298+789===1300-2+800-11=2100-3=2087

=1300-2+700+89
=2000+87
=2087

1298+789
=1298+2+700+87
=1300+700+87
=2000+87
=2087

1300+790-3