By next month he have been working in our factory for 30 years

问题描述:

By next month he have been working in our factory for 30 years

到了下个月,他已经在我们工厂工作了30年。

到下个月我们已经在我们工厂工作30年了。

到下个月他就在我们工厂工作了30年了
注意have要改成will have