Ever since I took 2 years of Latin 9-10 years ago I never get it wrong. In Latin the pronunciation makes it obvious. Necesse est means "it is necessary" and it is pronounced "Nekesä" more or less (short e). The only thing you have to remember is double s, because it sounds essentially the same, which after seeing it spelled the same in two languages is easy.
rex, regis, regi, regem, rege, rex (singular) reges, regum, regibus, reges, regibus, reges (plural) In order: nominative, genitive, dative, accusative, ablative, vocative But believe me, you could do worse than studying Latin. Latin has 6 cases (and a 7th called locative that only applies to some words), x2 for plural = 12 forms. Finnish has 15 singular cases (30 total) and Turkish has 16 total. Also, 2 of the Finnish cases can have 2 different forms depending on context. Hungarian, if I remember correctly, has 18 singular (36 total) cases and 6 additional possessive forms in the singular (12 total) for a grand total of 48 case forms for nouns. Though, not all nouns have all 48 (most have 46).
I wonder how many people have requested it on the Incubator? :) Would be difficult to add, however—they could add TTS snippets for it, but the question would be which pronunciation set to use? Eg, Ecclesiastical Latin is just plain wrong, but widely used, and Oxbridge Latin isn't even spoken with an accent at all.
Personally, I go with the current Italian standard for Latin pronunciation (as I was taught Latin by a lovely Italian lady called Lucia), which has as its most basic rule that it should sound like playing a flute: "tu te ki ke" rather than "tu te chi che". Even without a spoken variant, it would be nice to have to brush up with. :)
It ends in 'g' when it refers to an En word. (Example: En nödvändig vakt / Vakten är nödvändig).
It ends in 'gt' when it refers to an Ett word. (Example: Ett nödvändigt kaffe / Kaffet är nödvändigt).
And it ends in 'ga' when it refers to a plural word. (Example: Två nödvändiga kvinnor / Kvinnor är nödvändiga).
It also ends in 'ga' when it comes before a definite noun (Example: Den nödvändiga vakten).
Hope that helps!
there's seems to be a bug in the duolingo system. I've been doing the lesson on my computer and when you type the words it's important not to make any typos or mistakes (nödvändigt instead of nödvändig) or it will be considered wrong, however, when using the word bank and clicking on nödvändigt instead of nödvändig, it results in a correct answer but just a 'typo'. Given that not using the word bank is harder/more difficult, it's should be judged easier, no? Or at least equally strict...