How do you decide which of two numbers is greater when both numbers are positive?

If x - y > 0, then x is greater than y.
The greater positive number is the one further from zero.

Which number is greater can be worked out on a digit by digit basis:

To compare numbers starting with the highest place value column compare the digits, moving right a place value column until either all digits have been considered or one digit is higher than the other - the number with the higher digit is the greater number. (If a place value column is empty, its digit value is 0).