Final answer:
To make 12 1/2 of a batch of bread, you will need approximately 166 2/3 cups of butter.
Step-by-step explanation:
To calculate the amount of butter you need, first find the amount of butter needed for one batch (13 1/3 cups). Then, multiply this amount by the fraction of a batch you want to make (12 1/2).
Step 1: Convert the mixed number 13 1/3 to an improper fraction: 13 1/3 = 40/3.
Step 2: Multiply the improper fraction (40/3) by the fraction of a batch you want to make (12 1/2 = 25/2).
Step 3: Simplify the resulting fraction, if necessary, and convert it back to a mixed number, if desired. The final answer is approximately 166 2/3 cups of butter.