It is not 12. It is 18. Typing the series into a calculator in sequence is not a correct approach, since the question was phrased in English. Since the word "multiply" was used, not "multiplied", it denotes a present tense command which applies to the entire portion of the sentence immediately preceding it (3+3), which equals 6, so the sentence is instructing the reader to multiply that sum by 3, which equals 18. If the sentence is translated into mathematical terms, it would be (3+3)x3. However, since it seems that few nowadays know correct English, it wouldn't be expected that many would interpret it this way.
Eager Otter wins the title (whatever it is lol). Of course, some leeway in translation had to be taken, since the question was not posed in correct English, but it was obviously attempted to be posed in English rather than in strictly mathematical terms.