Someone help me solve this and could you explain why too?

3.5

Step-by-step explanation:

Well its easiest to just plug in the answers and see like 2 times 3.5 is 7.

Another way is saying 7 divided by 2 is 3.5

then u check to make sure its the same for all the numbers.

Which it is because 21 divided by 6 is also 3.5 :)

correct answer:

i^31 = -i

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