<style>
    .ib {
        display: inline-block;
    }

    .label {
        display: inline-block;
        border: 1px solid black;
        font-size: 20px;
    }

    button {
        display: inline-block;
        border: 1px solid black;
        background-color: transparent;
        font-size: 40px;
    }
</style>

<div class="ib">
    <div class="label">A</div>
    <button>
        <div>B</div>
    </button>
</div>