hard/tough nut to crack
sth.difficult to understand or to do 难事;棘手的问题
The girl found the algebra lesson was a hard nut to crack.这女孩发现代数课难以应付。
Dealing with that problem was a hard nut to crack;you must have worked hard to solve it.处理那个问题很难,你一定花了很大的气力。
hard put(to it)
in a difficult position;faced with difficulty面临困境;为难
The little girl found herself hard to put to it to find the way home.这小女孩发现她认不得回家的路了。
We were hard put to it to solve this problem,but we succeeded at last.我们起先对解决这个问题感到很为难,但最终还是圆满解决了。