In English it is correct to say
Miikka and Joni know how to DANCE tango
Tango is a style of dance. People do not just ballet, they dance ballet. In fact, saying that the miikka and joni know how to tango would suggest the slang for tango which is to fight or to know how to play or do something a certain way.
Ironically it is this sentence and similar phrases that are the reason why you should include the dance word.
We don't want tango to mean what it does in "it takes two to tango" we want it to mean the dance. So for absolute clarification and the most accurate translation, you include the word dance just like they did in Finnish.
Ehhhhhh, but "it takes two to tango" is an idiom literally meaning "it takes two people to dance the style of the tango" but figuratively meaning "it takes two people to do _ thing we are talking about (fight/play tic tac toe in a tent after marriage/etc." I'd (American) actually say they can "do the tango." But I'd probably also say "they can tango" just like I'd say "they can waltz" or "I've always wanted to learn tango/how to tango!"
I translated it as "Miikka and Joni are able to dance the tango." and got marked wrong. Is this truly an incorrect/inaccurate translation or a correct alternative answer that has not been added?
I ask this because in other questions, I have seen translations that are apparently correct to me but turn out having subtle differences in Finnish and justifiably should be translated differently.
I would say that osata is quite specifically to know how to do something. Voi or voida is more that you can do something.
"Osaatko istua" - "do you know how to sit" could be a remark made to a kid who won't sit still in class or something
"Voitko istua" - "can you sit" you are just asking the person to sit down
"Pystytkö istua" - "are you able to sit" this implies the persons health may interfere with the ability to sit and you are asking if its even possible for them at all. It could be used as a sassy but more polite remark to that kid who can't sit still in class but it is fundamentally different from the other
In this case it is okay, it is probably debatable. But you can always just be more specific by translating more directly to avoid failing questions