Final answer:
To estimate the difference between decimals and express it as a whole number, round the decimals to the nearest whole number and subtract them.
Step-by-step explanation:
When estimating the difference between decimals and expressing the answer as a whole number, it is important to pay attention to significant figures. In the given example of 12.656 - 5.006, we can round both numbers to the nearest whole number. This would give us 13 - 5 = 8 as the estimated difference.