* {
    box-sizing: border-box;
}

.flexbox {
    display: flex;
    flex-wrap: wrap;
    width: 350px;
}

.box {
    border: 1px solid black;
    padding: 20px;
    margin: 5px;
}

.red {
    background-color: red;
    width: 70px;
}

.blue {
    background-color: aqua;
    width: 200px;
}

.yellow {
    background-color: yellow;
    width: 280px;
}