A common denominator, though not the least, is 7500.
If I wanted to be nasty about it, I would say 1, because the least common denominator of 45/1 and 75/1 is 1. The least common denominator of two fractions is the least common multiple of their denominators. I presume you are asking for the least common multiple of 45 and 75, which is 225.
A common denominator is 75.
The LCM is: 525
There is no such thing as a most common denominator.
375 (which is 3*125 or 75*5).
The LCD is 600. Since the pair have no common prime factors, the LCD is the product of the two. 8 x 75 = 600
There is none because the Least Common Denominator (or LCD) is the Least Common Multiple (LCM) of the denominators of two or more fractions. Even if you converted your numbers (x) to their fraction equivalents (x/1), the LCD will always be 1.
It is any multiple of 75.