How do you turn this fallacy into a valid agrument:seeing that all teenagers are irrational and make poor decisions parents should make their decisions.

Answer 1

It's obviously a vast generalization!
http://writingcenter.unc.edu/resources/handouts-demos/writing-the-paper/fallacies

Be sure to read through the other fallacies explained here and concentrate on the Tip section under the one(s) that seems/seem appropriate. There are many ideas in those tips to help you correct different fallacies.

I would ask you these questions about this statement:
1. What proof is there that "all teenagers" ... ?
2. What proof is there that all parents make good decisions and should therefore make decisions for their teenagers?

What questions would you ask, after reading the Tip section under "Hasty generalization"?

Answer 2

Also, in writing any argument, be sure to bookmark this website:
http://www.powa.org/

Make extensive use of the first four tabs across the top plus the Argumentative Essays tab.

Answer 3

Thank you you provided so great websites I am still a little unsure of what steps would best help me make this a valid agrument. Thank you for help any more assistance is greatly appreciated.