Mio is not correct. The way we compare numbers is to start with the greatest place first and compare the digits in that place. If the digits are the same, move on to the next digit to the right. In this case, the digit 3 is in the millions place in both numbers. So compare the digits in the hundred thousands place. The digit 4 is in the hundred thousands place in 3,499, 999. The digit 9 is in the hundred thousands place in 3,921,012. 9 is greater than 4 so 3,921,012 is greater than 3,499,999.