The least common denominator (LCD) is 1.
LCD(8, 20, 15) = 120
A common denominator of 20 and 30 is 600. This is NOT the least common denominator, though.
The is no "largest" common denominator. For any denominator you find, we can multiply it by a natural number and come up with a larger one. Do you mean LEAST COMMON DENOMINATOR?
Least common denominator is used for fractions, not integers. Integers can be expressed as fractions, though, by placing them over 1 so if you really meant least common denominator then the answer is 1. If, however, you meant least common multiple, then then answer is 60.
A common denominator, though the least, is 260.
It is: 20
A common denominator, though not the least one, is 12*20 = 240.