The answer is 1
The least common denominator (LCD) is 1.
LCD(63, 7) = 63.
85-63 = 22
LCD(9, 21) = 63
126
63
It is: 315
252
63
It has to be 7x9 or 63 or less. There is no number less than 63 which is divisible by both 7 and 9 therefore 63 is the LCD.
The LCD (Lowest Common Denominator) of 7 and 9 is 63.
It is: 63