If you want to say "Nine is less than a number k," you would write 9<K. If you're asking for an equation, e.g. "Nine less than a number k is equal to that number divided by three," you would write k - 9.
The number is 909110001 is a number. To write this number out in words it would write out at nine hundred nine million, one hundred ten thousand, and one.
You would write it 2,609.
12.9 IS a decimal number. It is twelve and nine tenths.
999,999,999.....nine hundred ninety nine million, ninehundred and ninety nine thousand, nine hundred and ninety nine
It would be written 902,020
One thousand, nine hundred twenty-eight and seven hundredths.
The number 99 would be spelled ninety-nine.
12.9 IS a decimal number. It is twelve and nine tenths.
67.915 = sixty-seven and nine hundred fifteen thousandths.
It would be written as 350,359
There is no selected number so it would be a variable. The answer is 2n-9 (n is the number which you choose)