It is an almost insoluble problem.

这几乎是一个不可解决的问题。

youdao

We couldn't finish the insoluble problem given by our teacher.

我们没法解决老师给的那个不能解决的问题。

youdao

I pushed the problem aside; at present it was insoluble.

我把这个问题放到了一边；目前它是无法解决的。

《柯林斯英汉双解大词典》

In every case, humanity and common sense made the insoluble problem just get up and go away.

NEWYORKER: The Caging of America

On the practical side, the insoluble problem is slippage over time.

FORBES: U.S. Government: Too Big To Succeed?

The opening of the sacristy is one of several projects through which today's 25-strong Orthodox Christian fraternity is attempting, with considerable subtlety, to solve an almost insoluble problem.

ECONOMIST: Saint Catherine's monastery