I would suggest that a similar phrase would be: Average Joe
An excerpt from Wikipedia's page on the term includes:
used primarily in North America to refer to a completely average person, typically an average American. It can be used both to give the image of a hypothetical "completely average person"
In the example given in your question, it would be used like:
The average Joe can solve this problem.
Or some similar phrasings:
Your average Joe can solve this problem.
Any average Joe can solve this problem.
Or sometimes if spoken:
Any ole average Joe can solve this problem.
Kirt mentions "Joe" in their answer, but I think that specifically an "average" Joe is equivalent.
"Average Joe" is on this list of terms referring to an average person, on which is also found "Tom, Dick, and Harry": https://en.wikipedia.org/wiki/List_of_terms_referring_to_an_average_person