123+234+345-456+567+678+789-890=．

Question

123+234+345-456+567+678+789-890=______．

Answer 1

123+234+345-456+567+678+789-890
=123+123+111+123+111×2-（123+111×3）+123+111×4+123+111×5+123+111×6-（123+111×7-10）
=123×（3-1+3-1）+111×（1+2-3+4+5+6-7）+10
=123×4+111×8+10
=123×2×2+111×2×4+10
=（123+222）×4+10
=345×4+10
=1390；
故填：1390．