You have a 1/6 measuring cup, and you need 6 of it to have 1 full cup.
The recipe needs 13 and 1/6 cups.
Since for every 1 full cup, you will need 6 times of 1/6 measuring cup.
Multiply this by 13, we have :
6 x 13 = 78
You will need 78 times of 1/6 in order to have 13 cups and another 1 of 1/6 measuring cup.
Therefore, the answer is 78 + 1 = 79