*{
    box-sizing: border-box;
}

body {
    background-image:url("../img/pattern.gif");
}

.padre{
    width: 80%;
    height: 600px;
    background-color: grey;
    margin: 20px auto;
    border: 5px solid black;
    display: flex;
    flex-wrap: wrap;
}

.hijo1{
    width: 96%;
    height: 150px;
    margin: 20px auto;
    background-color: lightgrey;
    border-bottom: 12px double black;
    text-align: center;
    font-size: 4em;
    padding-top: 30px;
}

.hijo2{
    width: 30%;
    height: 250px;
    margin: 20px auto;
    background-color: lightyellow;
    padding: 20px;
    font-size: 2em;
}

.hijo3{
    width: 30%;
    height: 250px;
    margin: 20px auto;
    background-color: lightskyblue;
    padding: 20px;
    font-size: 2em;
    text-align: center;
}

.hijo4{
    width: 30%;
    height: 250px;
    margin: 20px auto;
    background-color: pink;
    padding: 20px;
    font-size: 2em;
}