math

set up the proportion

 

6 yards= 18 feet= 216 inches

 

so

 

216        1

-----  =  -----

8.64       x

 

then you cross multiply to find x (8.64 * 1)/216 =0.04

 

so the price per inch is 4 cents per inch

1 yard = 36 inches

6 yards = 216 inches 

then divide 8.64 by 216 (8.64/216) = 0.04

1 inch = 0.04cents

 

to check answer just multiply 216 by 0.04 and you wil get 8.64.