The LCD (least common denominator) is the smallest number that can be a common denominator for a set of fractions.
Start by finding the lowest common multiple (LCM) of the denominators 4x and 5x, the LCM is 20x as:
[tex]\begin{gathered} 4x\times2=8x \\ 4x\times3=12x \\ 4x\times4=16x \\ 4x\times5=20x \\ \text{and} \\ 5x\times2=10x \\ 5x\times3=15x \\ 5x\times4=20x \end{gathered}[/tex]
The LCD is the same LCM of the denominators, then the LCD is 20x
