There are a couple ways you can solve this. You have a price for every 3 yards, you have a total purchased of 24 yards. You can either figure out the price for 1 yard and multiply that by 24. Or you can divide 24 by 3 to find out how many sets of 3 yards Aubrey bought.
If you try to find the price for one yard:
we have the price for 3 yards is 6.33 so 3y=6.33 We divide each side by 3 and we get y=2.11 so 1 yard is $2.11, Aubrey bought 24 yards so we need to multiply the price for 1 yard by 24. so 2.11x24= $50.64
Lets solve it now by figuring out how many sets of 3 yards Aubrey bought and figuring out the price from there. So, we know the price is for every 3 yards. 24 is divisible by 3 and equals 8. So Aubrey bought 8 sets of 3 yards of ribbon. 8 sets at a price of 6.33 per set. We now multiply the set price by the number of sets. 8x6.33 equals $50.64
Notice the answers are the same, we just went about finding them in different ways.