Why is the particle と being used in the following sentences?

Question

I'm reading the JLPT N3 読む guide and the explanation for the conjunction ただ says this:

前の文の内容と違うことがあると付け加えて説明する。

Also, there's a section where the next sentence appears:

台風が接近しています。そのため、明日の旅行は中止となりました．

Why is と being used for this?

Answer 1

前の文の内容と違うことがある...

「～～と違う」 means "is different from ~~".

The と in ～と違う indicates 「比較・類別の際に照合される相手」(明鏡国語辞典) or 「比較の基準」(#3 in デジタル大辞泉). It's used with a word that expresses difference, similarity, identity, or comparison, such as 同じ, 違う, 異なる, 似る, 比べる, etc. Eg:

～と同じ -- is same as~~
～と異なる -- differs from~~
～と似ている -- is similar to~~
～と比べる -- compare with~~

Related thread: How is と used in these sentences?

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The と in ～と付け加えて説明する is quotative.

『前の文の内容と違うことがある』と付け加えて説明する。
lit. (The word ただ is used to) additionally explain that there's something different from (something that deviates from / doesn't agree with) the content of the previous sentence.

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明日の旅行は中止となりました。

～～となる (≂ ～～になる) means "become ~~." The と marks the result of change.

中止となりました means lit. "became cancellation" → "was cancelled"

_{Your example can be rephrased as 明日の旅行は中止になりました without changing the meaning. 中止となりました sounds a bit more formal than 中止になりました.}

～となる and ～になる are not always interchangeable. For more, see: What is the difference between 〜となる and 〜になる?

Answer 2

前の文の内容と - With the content of the previous sentence

Noun +　と - with(noun)

友達と - with friend

違うことがあると - If there is a difference

jisho + と - if(verb)

そこに行くとーIf you go there

付け加えて説明する - Add explanation

前の文の内容と違うことがあると付け加えて説明する。

literally it means

If there is a difference With the content of the previous sentence Add explanation

Answer 3

Disclaimer: regarding your second question only (please consider splitting your question in two different ones).

The following patterns are very similar an both mean "A becomes B":

Aは Bになる

Aは Bとなる

The difference between them is that 「AはBとなる」 implies that B is the final state reached by A, whereas 「AはBになる」 does not.

For example:

昔はこの辺に畑がたくさんあったものだが、今はすっかり住宅地【じゅうたくち】となった。 Long ago, there were plenty of fields in this area. Now, it has completely turned into a residential district.

It is very unlikely that the area changes to a different kind of place in the future, therefore it is its final state and となる is used.

Similarly, in the sentence of the question

明日の旅行は中止となりました。 The trip tomorrow has been cancelled.

the trip has been cancelled。Since 「となる」 is used, we can infer that the possibility of uncancel the trip is very unlikely as "cancelled" is regarded as the final state of the trip.