Suppose the leftmost digits of two numbers are 8 and 3. can you tell which number is greater? explain.

No, you can't. This is by knowing the concept of place values. Place values are the values each digit of a number holds. It increases as you go from right to left, such that the largest value is the leftmost digit. It is given that 8 is greater than 3. However, the number of digits of the number may differ. For all we know, the numbers might be 800 and 3,000. In this case, 3,000 is much larger even though digit 8 appears to be quantitatively greater.