The estimate is 5 while the difference is 4.3
Here, we want to find the estimate the difference and also get the real difference between the two numbers
To get the estimate, we round up each of the numbers to the closest integer
When we talk of an integer, we mean the nearest whole number
Thus, 8.5 becomes 9
while 4.2 becomes 4
The estimated difference is thus 9-4 = 5
However, the actual difference is what we have when we actually make a direct subtraction
Thus, mathematically, we have this as 8.5 - 4.2 = 4.3