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Question
Find n, if: `((15 - "n")!)/((13 - "n")!)` = 12
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Solution
`((15 - "n")!)/((13 - "n")!)` = 12
∴ `((15 - "n")(14 - "n")(13 - "n")!)/((13 - "n")!)` = 12
∴ (15 – n) (14 – n) = 4 × 3
Comparing on both sides, we get
15 − n = 4
∴ n = 11
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