Is this what you are thinking?
Note divs one, two, three need to be right after each other otherwise you will get a funny spacing(div three will drop to a new row).
<div style="width:480px; border:1px solid purple; ">
<div style="width:40%; display:inline-block;">First</div><div style="width:20%; display:inline-block;">Second</div><div style="width:40%; display:inline-block;">Third</div>
</div>