To determine how much flour was used during the day, we can subtract the amount of flour left at closing from the amount at the start of the day.
Starting with 30 pounds 8 ounces, we convert the pounds to ounces and add the initial ounces to get the total initial amount in ounces:
30 pounds = 30 * 16 = 480 ounces
480 ounces + 8 ounces = 488 ounces
Next, we do the same conversion for the amount left at closing, which is 12 pounds 5 ounces:
12 pounds = 12 * 16 = 192 ounces
192 ounces + 5 ounces = 197 ounces
Finally, we subtract the amount left at closing from the initial amount to find how much flour was used:
488 ounces - 197 ounces = 291 ounces
Therefore, the bakery used 291 ounces of flour that day.