120.
First you need a common denominator: 3/4 and 5/8, the common denominator is 8. (4x2=8, 8x1=8) Multiply both the numerator and denominator of 3/4 by 2 so that it becomes 6/8. Now that a common denominator is established, you may subtract them with ease. 6/8 - 5/8 = 1/8.
There is none because the Least Common Denominator (or LCD) is the Least Common Multiple (LCM) of the denominators of two or more fractions. Even if you converted your numbers (x) to their fraction equivalents (x/1), the LCD will always be 1.
LCM(14, 6, 8) = 168
To find a fraction equivalent to 3/4 with a denominator of 8, you need to multiply both the numerator and denominator by the same number. In this case, you would multiply both 3 and 4 by 2 to get 6/8. Therefore, the fraction equivalent to 3/4 with a denominator of 8 is 6/8.
A common denominator, though the least, is 48.
The least common denominator for fractions with those denominators (11, 8 and 6) is 264.
The least common denominator of 6,7, and 8 is the least common multiple of those numbers. This is 168.
The least common denominator (I think you mean least common multiple) of 2, 8, and 6 is 24. 24 is perfectly divisible by 2, 8, and 6, leaving no remainder in any case.
There is none because the Least Common Denominator (or LCD) is the Least Common Multiple (LCM) of the denominators of a pair of fractions.
24
168
48
72
120
A common denominator of 6, 8 and 10 is 480. This is NOT the least common denominator, though.
120