JSFiddle - React, Tailwind, and code Playground

HTML

<div class="one" >
    
</div>


<div class="two">
    
</div

CSS

.one{
    border: 1px solid green;
    width: 29%;
    float:left;
    height:100px;
}


.two{
    border: 1px solid blue;
    width:69%;
    float:right;
    height:100px;
}

@media (max-width:767px) { 
    .one{
        width:100%;
}
    .two{
        width:100%;
}
}