selenium to read text contained in tile image and click on a button

I have a web page with contents like tile images which includes some text content and an image in it. In my application user will enter a text in a text box. What I want to do using selenium is that I want the text to be read somehow which is displayed in that tile image and if it match with the user entered text then I need to click on the button displayed below.

The tile image text has got same "classname" for all tile images and the button has got unique id's. But since I cant predict user entered text, I cant use ID in my application.

For your understanding, I am posting html code for both.

HTML Code for tile image text:

<span class="rm-displayBlock rm-marginBottom5px rm-fontWeightBold largeTileTitle rm-textOverflowEllipsed">10monkeys.com Maths (FULL)</span>
HTML Code for Button:

<a href="JavaScript:;" appid="f03a1962-38fc-e1f5-cee1-a8a9ce4684a5" id="d70e5839-a9cd-b86f-cba5-3c41cd0826fe" class="btn btn-primary rm-floatLeft">Buy</a>

How can I achieve What I said? Any comments would be really appreciated..