#### Answer

If there are six candidates, 15 comparisons must be made.

#### Work Step by Step

Suppose that the pairwise comparison method is used to determine the winner in an election. In an election with $n$ candidates, the number of comparisons, C, that must be made is determined by the formula $C = \frac{n~(n-1)}{2}$
We can find how many comparisons must be made if there are six candidates. In this case, $n=6$.
$C = \frac{n~(n-1)}{2}$
$C = \frac{6~(6-1)}{2}$
$C = 15$
If there are six candidates, 15 comparisons must be made.