*{
    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;
    padding: 10px;
}
#hijo2{
    width: 100%;
    height: 230px;
    background-color:pink;
    margin-left: 10px;
    padding: 10px;
}
#nieto{
    width: 98%;
    height: 210px;
    background-color:blue;
    margin-left: 10px;
    padding: 10px;
    
}