3x2=7 5x4=23 7x6=47 9x8=79 10x9=?

which means
which means
which means
which means

That's the patter we have here, but last one is which does not follow the pattern because first number is even and another is odd, which means that we can't implement pattern above to this situation, therefor we can check other side of the pattern.

which means
which means
which means
which means

and  is the number you are looking for.

So fulfilled pattern you need to take in consideration would be:

which means
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which means
which means
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which means
which means
which means