Answer: 1/6.
Step-by-step explanation: When rolling a 6-sided die twice, there are 36 possible outcomes (6 outcomes on the first roll multiplied by 6 outcomes on the second roll).
To calculate the probability of rolling a sum of 7, we need to count the number of ways that can happen. There are six possible ways to roll a sum of 7: (1,6), (2,5), (3,4), (4,3), (5,2), and (6,1).
Therefore, the probability of rolling a sum of 7 is 6/36, or simplified, 1/6.