The best way to estimate a quotient using compatible numbers is to first understand how compatible numbers work. They are numbers that are close in value to the actual numbers and are easily added, subtracted or divided.
Compatible Numbers numbers that are easy to compute mentally are called
Suppose you are asked to evaluate a quotient like 923/462. You have several options. You could choose 900 and 500 as compatible numbers for the two given numbers and then your estimated quotient would be 900/500 = 1.8. Or You could choose 920 and 460 as the compatible numbers for them and then your estimated quotient would be 920/460 = 2.0. So the question is essentially, what compatible numbers did you pick and using them, what was the quotient. There is no correct answer to picking compatible numbers. Any estimation is a trade-off between simplicity and accuracy. Incidentally, a more accurate answer is 1.9978 (approx), but even that is not perfect!
535.6 divided by 35 using compatible numbers = 15.302857142857144
Estimate 43/81 by using compatible numbers
35000 ÷ 70 = 500
"Quotient" implies that there is some sort of division going on. I don't see any evidence of that.
The quotient will be positive.