Answer:
15 3/4 yards of fabric for 7 elf costumes
Explanation:
So we can agree that 6 3/4 yards of fabric = 3 elf costumes
So if we divide 6 3/4 by 3 you get 2 1/4
2 1/4 yards of fabric = 1 elf costume
so if we do 2 1/4 * 7 we get 15 3/4 yards of fabric for 7 elf costumes