Muslim women giving talks in gatherings where non-mahram men are present
Question

                is it allowed for a brother to organise i talk and the speaker is a sister. 
the issue is on women in islam but the sister is talking to every on (brothers and sister)i thought it's not but the organisors say it is allowed but they ask for evidence is there any on this issue
Praise be to Allah.We
      put this question to Shaykh ‘Abd-Allaah ibn Jibreen (may Allaah preserve
      him) who answered as follows:
 In
      our opinion this is not permissible except in cases of necessity, and on
      the condition that the men cannot see her. There should be a screen
      between her and them, and she should not soften her voice too much,
      because her voice may be ‘awrah. Women are not allowed to say Tasbeeh
      out loud in the prayer – if the imaam makes a mistake – instead they
      are commanded to clap [to draw the imaam’s attention to a mistake], lest
      their voices be recognized.
Shaykh ‘Abd-Allaah ibn Jibreen
 At
      this point we would ask the brothers who are organizing these lectures:
      what need is there for a woman to give a lecture in front of a group of
      people which includes men? We hope that the answer will not be because
      they want to prove that Islam does not oppress women or to prove that they
      are open-minded and enlightened! Or any other weird and mistaken reasons
      that can never be used to justify opening the doors to fitnah (temptation)
      which Islam seeks to shut firmly. We constantly repeat our advice:
      organize your activities within the framework of sharee’ah. And Allaah
      is the Guide to the Straight Path. And Allaah knows best.