Question

What did the 12 tables do fro the rights of plebians?

Who could vote in rome?

Answer 1

This article answers your first question. Read the summary of a few of the tablets near the end.

http://www.socialstudiesforkids.com/articles/worldhistory/twelvetables.htm

Check this article for the answer to your second question.

http://oncampus.richmond.edu/academics/education/projects/webunits/greecerome/Romegovt1.html

Answer 2

Here are articles on the Twelve Tables of Roman law:
http://www.google.com/search?hl=en&as_q=twelve+tables+rights+plebians&as_epq=&as_oq=&as_eq=&num=10&lr=&as_filetype=&ft=i&as_sitesearch=&as_qdr=all&as_rights=&as_occt=any&cr=&as_nlo=&as_nhi=&safe=images

Articles on who could vote in Rome:
http://www.google.com/search?hl=en&lr=&as_qdr=all&q=who+could+vote+in+rome