Answer:
y = 9/4x, 15_3/4
Step-by-step explanation:
Convert 6_3/4 to 27/4
3 costumes need 27/4 yards
1 costume needs 9/4 yards
y = 9/4x
x is 7. amount needed: y = 9/4(7) --> y = 63/4 = 15_3/4
