In order to assess each of the deals equally, one has to know the price per yard of the given items.
1. 6.5 square yards for 6.26
n1 = 6.26 / 6.5 square yards
n1 = 0.963/square yard
2. 4 square yards for 3
n2 = 3/4 square yards
n2 = 0.75/square yard
3. 8.5 square yards for 8.1
n3 = 8.1/8.5 square yards
n3 = 0.953/square yards
4. 6 square yards for 7.2
n4 = 7.2/6 square yards
n4 = 1.2/square yard
From least to greatest the order would be 2,3,1, and 4.