A common denominator of 20 and 30 is 600. This is NOT the least common denominator, though.
A common denominator, though not the least one, is 16*24 = 384.
A common denominator, though not the least, is 1680.
A common denominator, though not the least one, is 12*20 = 240.
A common denominator, though the least, is 260.
120
21/24 and 20/24
11 over 24 (11/24) Here's how: You need to find a common denominator. The lowest common denominator is 24, but you can use any common denominator to subtract. So convert 5/6 to 24ths: multiply numerator and denominator by 4 = 20/24, then multiply numerator and denominator of 3/8 by 3 = 9/24. Now subtract 9 from 20 = 11, which is the numerator of the difference: 11/24. This is already in simplest form.
A common denominator of 20 and 30 is 600. This is NOT the least common denominator, though.
If those are all denominators, the LCD is 360.
A common denominator is 72.
A common denominator 24.
A common denominator, though not the least one, is 24*21 = 504.
A common denominator, though not the least one, is 16*24 = 384.
The greatest common denominator is infinite.
A common denominator, though not the least, is 240.
A common denominator, though not the least, is 1680.