As we know that the promoter is present in the start of a gene i.e. at 5' and RNA polymerase attaches on promoter to start mRNA synthesis. If it so, then, when RNA polymerase start its function to form mRNA it should be synthesize from 3'-5'.

e.g.

5' CGAGGTCC 3' is a gene sequence then promoter region is present at 5' which allows RNA polymerase to attach. Then RNA polmerase moves from 5'-3', if it is so, then in which direction mRNA should synthesize?

I think you should ask the Mods to post this in the "Homework" thread. and then refer to this:

 

http://highered.mheducation.com/sites/0072507470/student_view0/chapter3/animation__mrna_synthesis__transcription___quiz_1_.html

 

It is explained simply. If you don't get it, someone will help you out.

It might help to think of reading the template and doing the polymerization as two separate things.