Respuesta :
9.990 is the greatest because 9.9 would have all 0's after it so it would be 9.90 which is less than 9.99 and 9.09 is less that 9.990.
9.99 > 9.9 > 9.09
9.99 is greater than 9.9 because 9.99 is greater than 9.9 by 0.09
9.99 is greater than 9.9 because 9.99 is greater than 9.9 by 0.09