Respuesta :

frika
Since
 [tex]18x^3=2\cdot 3\cdot 3\cdot x\cdot x\cdot x \\ \\ 30x^5=2\cdot 3\cdot 5\cdot x\cdot x\cdot x\cdot x\cdot x [/tex]
you can see that common expression is 
[tex]2\cdot 3\cdot x\cdot x\cdot x=6x^3[/tex].
Answer: Correct choice is A.