Breakdown of Við skilum svarblaðinu núna, er það ekki?
vera
to be
það
it / there (existential) / the one (n)
ekki
not
við
we
Questions & Answers about Við skilum svarblaðinu núna, er það ekki?
English question tags change depending on the sentence (e.g., "don't we?", "aren't you?"). Does Icelandic just use er það ekki? for all of them?
Yes! While English makes you match the helper verb and pronoun to the main sentence, Icelandic uses the fixed phrase er það ekki? (literally "is it not?") as a universal tag to mean "right?" or "isn't that so?".
Why is the answer sheet (svarblaðinu) in the dative case here?
It is because of the verb skila (to hand in / to return). This verb always forces its object into the dative case, regardless of what is being handed in.
How exactly is the word svarblaðinu broken down?
It is a compound word made of svar (answer) and blað (sheet/piece of paper). The -inu at the very end is the attached definite article ("the") for a neuter noun in the dative case.