Final answer:
The best estimate for the sum -15/16 + (-1/2) is -1 1/2, because the sum of these two negative numbers will be slightly less than -1 and a half.
Step-by-step explanation:
The question asks for the best estimate of -15/16 + (-1/2). To estimate this sum, we need to consider that these are both negative numbers and when added together will yield a number that is also negative and has a greater absolute value. The first term is just a little bit less than -1, and the second term is exactly -1/2. Adding these two numbers together should give us a result that is just a bit less than -1 and a half, because -15/16 is very close to -1 and will contribute almost another half when added to -1/2.
Therefore, the best estimate for the sum -15/16 + (-1/2) is -1 1/2.