HTML code for addon for input field

Input AddOn html

<div class="container">
    <h2>Input Addon</h2>
    <p>With FlexBox it is easy to place an add-on to the start of an input or
        a button to the end of an input. An add-on can be text or an image. An add-on
        is used to explain to a user what type of information should be put in the
        input field.</p>
    <hr>
    <h3>Example of Addon</h3>

    <div class="flexContainer marginBottom">
        <span class="entry">Amount</span>
        <input class="flexItem">
    </div>
    <div class="flexContainer marginBottom">
        <input class="flexItem">
        <button class="entry">Submit</button>
    </div>
    <div class="flexContainer marginBottom">
        <span class="entry">Amount</span>
        <input class="flexItem">
        <button class="entry">Submit</button>
    </div>

    <div class="flexContainer flexCenter itemCenter">
        <a href="index.html" class="homeButton">Return Home</a>
    </div>

</div>