Translation:I am nineteen years old.
I got a correct even thought I had typed "I am 17." and I am confused about it.
Duolingo just considers it as a typo since only one character is wrong. In early course if it asks for say 六 and you type 3 in the answer, since only one character is wrong it will count as valid with a typo.
Is there another way of saying "です"? When I'm watching people speak in Japanese I don't hear them saying it as often as I think it should
Yes, lots. It changes based on politeness level and conjugation (negative, past tense, etc). Also, many sentences end in verbs, rather than a copula.
If you want to say "X is Y", you will use a copula. If you want to say "X does Y", then you need an action verb.
Tôi đã nhận một chính xác thậm chí tôi nghĩ rằng tôi đã đánh máy "Tôi 8 tuổi". và tôi bối rối về nó