Question

how to estimate numbers​

Answer 1

The general rule for estimating is to look at the digit to the right of the digit you want to estimate. Estimating or rounding to the nearest whole number means looking at the digit to the right of the decimal. If you see a digit greater than 5, round up, and if it's less than 5, round down.

Answer 2

Estimation means guessing. So...uh...you have to guess the number.
Also, try to round it off to the closest fives.