* {
    box-sizing: border-box;
}

body {
    background-color: aqua;
}

#padre {
    width: 100%;
    height: 250px;
    background-color: blueviolet;
    display: flex;
    flex-wrap: nowrap;
    padding: 10px;
}

#hijo1 {
    width: 20%;
    height: 230px;
    background-color: lightgoldenrodyellow;
}

#hijo2 {
    width: 100%;
    height: 230px;
    background-color: pink;
    margin: 0 10px;
}

#hijo3 {
    width: 20%;
    height: 230px;
    background-color: lightskyblue;
}