"The high school assignments are difficult."

Translation: 高中的作业很难。

[michelle.ko]

There should be more flexibility in using/not using 的 - in most conversation it is dropped when the meaning is clear, such as in this sentence.

[EinMann694798]

Right

[EinMann694798]

You know Mandarin well!

[tasecho]

"the" is not needed

[varigby]

You are right

[livinicole]

Is it wrong to say 很难完成? I thought it would be a valid sentence meaning they are very hard to complete

[Gabrielle145359]

I don't think you can grammatically put the words in that order in Chinese.

[amythefan]

Hard should also work