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I am stuck and can't find anything on Google or SO. I have:

1+1+1+0 and I am asked to calculate the answer over GF(2).

My question: what answer?

I have no clue what to do. Can someone help me by telling me what I should do? Where do I start? Making an addition table? I honestly have no idea what they are asking or what is being expected.

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    The sum, I guess. Use that $GF(2)$ has characteristic $2$. – 2017-02-12
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    How are you defining $\mathrm{GF}(2)$? Are you using a book? (Hint: addition is done using modular arithmetic) – 2017-02-12
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    $GF(2)$ is the field of order $2$. See e.g. [Finite field](https://en.wikipedia.org/wiki/Finite_field). – 2017-02-12
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    There is no definition and no, not using a book. Just an assignment. @Bernard: the sum? I have no idea what characteristic 2 means. We have just one slide that explains it and I can see an addition table, that's it. No theory, nothing. That's why I am struggling. – 2017-02-12
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    okay, so you have an assignment to do this in $\mathrm{GF}(2)$, but no description of what this is? If you have a slide with an addition table, that should be all you need (it should tell you what $1+1$ and $1+0$ are). – 2017-02-12
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    Ah, yes... well, 1+1 = 0. So I assume this is all XOR. I get that, but I don't get what I should do with it or how to assume I can use that? It's not stated in the assignment that I can use it. – 2017-02-12
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    I assume you are supposed to use this to do the addition $1+1+1+0=((1+1)+1)+0$ – 2017-02-12
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    (if you are asking what you are allowed to use, that's a question for your instructor) – 2017-02-12
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    Thanks dear Morgan Rodgers. Question: how do you know I am supposed to do that? How did you recognize that? Could you explain, please? – 2017-02-12
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    @Siyah You add the numbers. You have an addition table. Which part is confusing? – 2017-02-13
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    I get 1+1 = 0, but the confusing part for me is the fact that we have 4 numbers. I don't know what "rules" we have when there are 4 numbers. What should I do? Just take the first two in parentheses? If so, why? I am trying to sort that out and that part is confusing, because I can't find info about it – 2017-02-13

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To answer my own question:

1+1+1+0 is the same as doing: ((1+1)+1) + 0 =

(1+1) = 0

(0) + 1 = 1

1 + 0 = 1

That gives me 1 as my answer. Thanks for helping me out Morgan Rodgers!