The phrase "a much harder problem" is correct and usable in written English.
It can be used when comparing the difficulty of a problem to another, indicating that it is significantly more challenging.
Example: "While solving the initial equation was straightforward, the next step presented a much harder problem that required advanced techniques."
Alternatives: "a significantly tougher issue" or "a considerably more difficult challenge".
Detecting which variable is in play is a much harder problem.
"But if you're trying to determine the pattern of a fingerprint, that's a much harder problem.
But over the next 20 years or so, the deficit will begin rising again — and this will be a much harder problem to address, because it is structural.
That's a much harder problem, though: if you don't trust someone, you also shouldn't trust anything that their computer tells you.
A much harder problem faces Unicode, the international standards organisation which most famously controls the introduction of new emojis to the world.
But getting good data for SEAmail becomes a much harder problem on the broader Internet than it is within an organization, Genesereth says.
Autism has turned out to be a much, much harder problem at every level of analysis than I think anyone expected.
On Tagged, we have to decide which 100 of 100 million users to recommend to you it's a different and much harder problem.
Turing envisaged a typed exchange between machine and person, so that a genuine conversation could happen without the much harder problem of voice emulation having to be addressed.More recently, the abilities of computers to play games such as chess, go and bridge has been regarded as a form of artificial intelligence.
Now a bill passed last week by the Legislature — and enthusiastically endorsed by Gov. Deval Patrick ��� aims to tackle the much harder problem of controlling health care costs.
Now scientists hope to show that T-cell therapy can work on the much harder problem of "solid" cancers, which have proved challenging to treat partly because of the difficulty of attacking all the cancer cells hiding deep inside each tumour.
