<body>
<div class="box floatLayout">
<div class="item i1"></div>
<div class="item i2"></div>
<div class="item i3"></div>
<div class="item i4"></div>
</div>
<div class="box flexLayout">
<div class="item i1"></div>
<div class="item i2"></div>
<div class="item i3"></div>
<div class="item i4"></div>
</div>
</body>
<style>
div.box{
width: 1080px;
outline: 2px solid red;
margin: 0 auto;
margin-top: 80px;
}
div.box .item{
width: calc(50% - 20px);
height: 300px;
}
div.box .i1{background-color: #fc0;}
div.box .i2{background-color: #f90;}
div.box .i3{background-color: #f30;}
div.box .i4{background-color: #99f;}
div.floatLayout{
overflow: hidden;
}
div.floatLayout .item{
float: left;
margin: 0 10px;
}
div.floatLayout .i3,
div.floatLayout .i4{margin-top: 20px;}
div.flexLayout{
display: flex;
justify-content: space-around;
flex-wrap: wrap;
row-gap: 20px;
}
div.flexLayout .item{}
</style>