VIXX is making us scratch our heads for another puzzle, but clever fans have managed to solve it in no time!

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The clues provided this time around involved less math than the last puzzle (good news for those of us who are not so good with numbers) and reads, "Key 2) VT EP. 15 / ULTIMATE MUSCLE." 

When you break the clues down, you deduce that in 'VIXX TV2' episode 15,

VIXXSG