There is none because the 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.
A common denominator, though not the least, is 7500.
It is any multiple of 75.
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.
It is 75.
75 (3 x 25, 15 x 5, 25 x 3)
1200
975
The Least Common Multiple (LCM) of 5, 15, and 75 is 75.
A common denominator is 75.
The Least Common Multiple (LCM) for 5 15 and 25 is 75.
The greatest common denominator, like the greatest common multiple, is infinite.
The LCM is 75.