To work out the problem is very hard .(同一句) _____ is very _____ _____ work out the problem .

It is very hard to work out the problem.
希望能帮到你,祝更上一层楼O(∩_∩)O
有不会的欢迎再继续问我(*^__^*)

it；hard to

_____ It is very _____hard _____ to work out the problem .

it hard to
真心希望帮到你啊

It hard to

It is very hard to work out the problem.

It hard to
祝你学习进步

IT hard to

To work out the problem is very hard . (同一句) it is very hard to work out the problem .

It,hard,to

It, hard to
祝你学习进步！
望采纳，多谢！

It is very hard to work out the problem.
这里是it做形式主语，真正的主语是hard后跟的不定式，以后要是遇到这类题，直接用It is加上形容词在跟不定式就行了。