Final answer:
To estimate the sum of the fractions 31/4, 17/3, and 8/18, you consider each fraction's closest whole number or obvious fraction, then add them up. The best estimate is more than 13 but less than 14, making 25/2 or 12.5 the closest option provided.
Step-by-step explanation:
The question is asking for the best estimate of the sum of the fractions 31/4, 17/3, and 8/18. To estimate the sum, we look at each fraction. The fraction 31/4 is close to 8 since 32/4 equals 8. The fraction 17/3 is more than 5 since 15/3 equals 5. Finally, the fraction 8/18 is less than 1/2 since 9/18 equals 1/2. Knowing this, 31/4 (approximately 8) plus 17/3 (more than 5) plus 8/18 (less than 1/2) would give a sum that is more than 13 but less than 14. Therefore, the best estimate from the given options for the sum is 25/2, which equals 12.5 (option c).