To find the least common denominator (LCD), you need to find the smallest multiple that two or more denominators have in common.
For example, if you need to add 1/3 and 1/4, you need to find the least common multiple (LCM) of 3 and 4, which is 12. So, the LCD is 12.
Another example, if you need to add 1/2, 1/3, and 1/4, you need to find the LCM of 2, 3, and 4, which is 12. So, the LCD is 12.
Therefore, the least common denominator depends on the denominators of the fractions you are trying to add or subtract.