"Best estimate' doesn't happen automaticallly, because you have to define "best" in this context. We could merely round all numbers and work with the results:
For example, starting with the work inside parentheses, we have:
5 5/6 - (1 + 4) = 5 5/6 - 5. We must round 5 5/6 up to 6. Then the "best estimate' is 6 - 5, or just 1.
