Translation:Thirty-eight days is nine hundred and twelve hours?
No, they don't, see the discussion at https://forum.duolingo.com/comment/24432784 and the links mentioned there, such as https://awelu.srv.lu.se/grammar-and-words/common-problems-and-how-to-avoid-them/subject-verb-agreement/sums-of-money-and-periods-of-time/ or https://erinwrightwriting.com/use-plural-singular-verbs-money/ or https://owl.english.purdue.edu/owl/resource/599/01/
Also see the comment by BrianSille2 below.
When the time periods are referenced as an interval we use the singular: Five days is too long. Twenty-five minutes is a new world record. Ten minutes is six hundred seconds.
"Long" is an adjective, the five days it describes is plural, so "are". "Record" is a noun, a singular and main noun, so it "is" twenty five minutes strictly speaking. At the end of the day it does not really matter, and in colloquial English one does find "is" and "are" interchangeable in these usages.
Hours of fun debating this one! I'm with 2FH3n0AZ, and I would say "Fourteen days are a fortnight" but conversely "A fortnight is fourteen days". I would say when the singular item is the subject it is probably "is" but when it is the complement it depends on the focus of the statement, despite what the grammarians say. And when both the subject and the complement are plural, as in the exercise, it should definitely be "are". However, I am also with Tom307502 in agreeing we must concentrate on the Czech.
I come in peace. Personally, I think it is silly to debate about whether the verb "should" be sing. or plural. The Moderator, a native CZ speaker, is letting you know how it is done in his language. That's all we need to worry about. Also, this verb issue is addressed in the Tips for this lesson.
I am here for a different question. The Tips says we should use Genative case for the counted item following numbers larger than four. However, in this sentence, the counted item is the subject, and subjects should be in Nominative case. So does this sentence teach us that the rule for numbers takes priority ?