Explanation:
First we have to find multiples of each of the denominators:
[tex]\begin{cases}20\rightarrow20,40,60,80,100\ldots \\ 15\rightarrow15,30,45,60,75,90\ldots\end{cases}[/tex]From those multiples we have to find which one is the least that is in both lists. In this case, the least number that's in both lists is 60
Answer:
LCD = 60