Explanation:
After you find the sums for each set, make a list, counting the number of ways a sum can occur.
You'll notice that for Set A, sums of 5, 6, 7, 8, and 9 all appear 4 times. So they have equal probabilities. In Set B, a sum of 7 appears 6 times. Sums smaller or larger than 7 are less common.
When we look at the data, we see that were more sums of 7 than any other sum. So this data was probably from Set B.