If `""^(n)C_(r -1) = 36, ""^(n)C_(r) = 84 " and " ""^(n)C_(r +1) = 126`, then find the value of `""^(r)C_(2)`.

Explanation

To solve the problem, we need to find the value of \( \binom{r}{2} \) given the equations:

1. \( \binom{n}{r-1} = 36 \)
2. \( \binom{n}{r} = 84 \)
3. \( \binom{n}{r+1} = 126 \)

### Step 1: Set Up the Ratios

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