The same as with two.
Example: 30, 42, 60
Factor them.
2 x 3 x 5 = 30
2 x 3 x 7 = 42
2 x 2 x 3 x 5 = 60
Combine the factors, eliminating duplicates.
2 x 2 x 3 x 5 x 7 = 420, the LCD
Say there's 2/3 and 1/2, it's called Least Common Denominator, so you need to look at the denominators which are 3 and 2.
Now list the multiples:
3: 1, 3, 6...
2: 1, 2, 4, 6...
As you can see both of them go into 6 the least amount of times because it's the one that they both can multiply.
Example: 1/30 and 1/42
Factor them.
2 x 3 x 5 = 30
2 x 3 x 7 = 42
Combine the factors, eliminating duplicates.
2 x 3 x 5 x 7 = 210, the LCD
By multiplication: 5*6*7 = 210
The LCD of 6, 5, and 7 is 210.
Multiply them together.
LCD(7, 5, 10) = 10
72
315
LCD is 24
The LCD of 567 and 5 is 2835The LCD of 5, 6, 7 and 5 is 210
The LCD of 6, 5, and 7 is 210.
210
140
The LCD of 7 and 77 is 77.
Multiply them together.
The LCD of 6 and 7 is 42
For 5/6 and 7/8 the LCD is 24.
LCD(7, 5, 10) = 10
The LCD of x, 5, 7, 15 is 105x.
LCD(5, 7, 25) = 175