15
72
the LCD of 2, 9 and 5 = 90
If that's 84 and 35, the LCD is 420.If that's 8/4 and 3/5, the LCD is 20.
The LCD, or Lowest Common Denominator, is the smallest multiple of each of the denominators of a set of fractions. So, assuming that 2, 4 and 5 are denominators of fractions (1/2, 1/4 and 1/5, for example), the LCD would be 20, because 20 is the lowest number that 2, 4 and 5 multiply into. So, your new fractions would be 10/20, 5/20 and 4/20. The purpose of finding the LCD is to allow for multiplying fractions together, or simply comparing them easily.
10
The LCD is 30.
5
30
60
18
28.
15.
30
LCD is 10 so: 9/10-5/10 = 4/10 = 2/5 in its lowest terms
18
The LCD is 10.