There is none because the Least Common Denominator (or LCD) refers to the Least Common Multiple (LCM) of the denominators of two or more fractions or mixed numbers. Even if you converted your whole numbers (x) to their fraction equivalents (x/1), the LCD would always be 1.
The common denominator is 28.
A common denominator, though not the least, is 168.
A common denominator, though not the least one, is 14*49 = 686.
A common denominator, though not the least one, is 14*12 = 168.
The least common denominator is 70.
There is none because the Least Common Denominator (or LCD) is the Least Common Multiple (LCM) of the denominators of a pair of fractions.
You need at least one more fraction in order to have a common denominator.
7.
168
126
98
Their product.