There is none because Least Common Denominator (or LCD) refers to the Least Common Multiple (LCM) of the denominators of two or more fractions or mixed numbers. Even if you converted your whole numbers (x) to their fraction equivalents (x/1), the LCD would always be 1.
If those are denominators, the LCD is 126.
The numbers 7, 3, and 2 share no common denominator. They are prime numbers.
1 is the only common denominator.
I suggest you do the following: 1) Find a common denominator of 5 and 7. (It need not be the least common denominator; multiplying the two denominators works for our purposes.) 2) Convert both fractions to equivalent fractions with this denominator. 3) Compare the numerators of the fractions thus converted.
The lowest common denominator of 5/42 and 7/30 is 210.
693
42
126
84
It is: 42
84
The least common denominator of 6,7, and 8 is the least common multiple of those numbers. This is 168.
1008
420
It is 630
126
42
84