Is it just me......or is it annoying to other people that Duolingo always comes up with an error when we enter "these" but the answer is "those"? Or vice versa. In English I don't think there's a really massive distinction between "these" and "those", a difference yes, but you'd still be understood ok. Maybe it would be better if Duolingo came up with a suggestion of how to improve the answer, rather than a full error and to make us do the whole sentence again. Similarly, there's the same issue when using "this" and "that" on Duolingo. Any thoughts?
I think the differences can be vague in both English and Czech, but here on Duolingo "ten, ti, tamten, tamti..." is mostly translated as "that, those" and "tento, tito..." as "this, these", isn't it?
"From how many people are those letters?"
This is another very odd sounding sentence, I think it would be written more appropriately along the lines of "How many people wrote/sent those letters?".
The answer shown above is grammatically correct, but it does sound odd in what I'd call everyday English. And so... "How many people are the letters from?" and "How many people are those letters from?" are also accepted. Your suggested alternative is not a translation of the Czech sentence in this exercise.
I wrote "those letters are from how many people " and it was not accepted but I believe it should have been.
To my AmE ear, "Those letters are from how many people?" suggests an element of surprise -- as if, for example someone has a huge pile of letters that, it turns out, where written by only two people. So I can see it as acceptable on the English side, but I would leave it to the CZ natives on the team to decide if it's true enough to the Czech sentence to be added.