You need at least two fractions to determine a least common denominator.
34
There is none because the Least Common Denominator (or LCD) is the Least Common Multiple (LCM) of the denominators of two or more fractions.
The LCD for 17 and 12 is 204
204
765
A common denominator, though not the least, is 1700.
You need at least two fractions to determine a least common denominator.
136
68
It is 85
119
Their product.
34
There is none because the Least Common Denominator (or LCD) is the Least Common Multiple (LCM) of the denominators of two or more fractions.
The LCD for 17 and 12 is 204
204