I am a newbies of this site. Please, help me to read the math expressions in "non-plain" text form like this:
$$a=\left(\sum_i y_i b^{x_i}\right) / \left(\sum_i b^{2x_i}\right)$$
What addin, application will help me to read this and other expressions in "normal" or professional (as msword mentions) form?
Thank you.
ADDED:
I saw this one:

And now I see this one: 
I have resolved this problem by using Google Chrome or Latex Composer add-on for Firefox and this editor