Is any factor of 9 or 3 as a denominator always to be a decimal.

No, it is not always a decimal. For example 3 is a factor of 9. If you have 3 in both the numerator and denominator the expression is equal to 1.0 which is a whole number, not a decimal number. A second example would be taking the factor 1 which could again equal 1.0 (when you divide 1 by 1).