If you're trying to type:
\(\displaystyle \sqrt[3]{54x} - \sqrt[3]{2x^4}\)
then I'm concerned that you called these square roots because they are not.
You did not ask any questions about this exercise, so I'm not sure where you're stuck. What have you done, thus far?
In
one of your other threads, wjm11 posted a link to some lessons about radicals, and how to work with them.
We are not set up to teach classroom material on these boards. My points is, we could spend time duplicating lessons for you, but if you do not understand the lessons that you've already seen, how could we know whether you would understand ours? That's too much of a potential waste of typing time for us and you.
Are you able to ask any
specific questions about the parts of your lessons that you do not understand? My point is, what exactly is it that you do not understand when you study? Make a list, if you need to. Let us know what you've thought about, in this exercise, and then we can determine where to begin helping you.
If you have trouble understanding your textbook's lessons or the lessons at the link provided by wjm11, then we can certainly find additional lessons on the same topic from many different authors, for you to see if anything clicks. Or, you can search for these yourself at Google, using a keyword phrase like
radicals simplify factor examples. If videos are more your style, check out khanacademy.org. Also, libraries have both math texts and librarians to help you find them.
If none of this helps you to ask a specific question, or to tell us
how we can help you, then you need a face-to-face tutor or a conference with your instructor.