What is a common denominator for 7 9 11?

The common denominator of any two or more whole numbers, such as 7 9 and 11, will always be one (1) because common denominators refers to the denominators of two or more fractions or mixed numbers, not whole numbers. So, a set of whole numbers (x,x) would have to be converted to their fraction equivalents, i.e., x/1, which will always yield a denominator of 1.