How do I determine which piece of fabric is the longest (2 3/4 yards of mink), 6 feet of silk), or (108 inches of Velvet)

To determine which piece of fabric is the longest, you need to convert all the measurements into a common unit. In this case, let's convert all the measurements into inches for consistency.

1 yard is equal to 36 inches.
1 foot is equal to 12 inches.
So, 2 3/4 yards of mink is equal to (2 * 36) + (3/4 * 36) = 72 + 27 = 99 inches.
6 feet of silk is equal to 6 * 12 = 72 inches.
108 inches of velvet remains the same.

Now, we have the following measurements:
Mink: 99 inches
Silk: 72 inches
Velvet: 108 inches

Comparing these measurements, we can conclude that the piece of fabric with the longest length is the velvet, as it measures 108 inches.