Question

What is the best estimate for 591.3 divided by 29

Answer 1

The answer is about 20.  600/30=20

Answer 2

The trick here is to round off the given numbers appropriately.
591.3 rounds up to 600 and 29 rounds up to 30.  600/30 = 20.  The whole point here is that you want a quick estimate, not an exact answer.