*{box-sizing: border-box; margin: 0; padding: 0;}

.contenedor{ max-width: 75rem; margin: auto;}
header {
    background-color: aquamarine;
    width: 100%;
    height: 9rem
}

nav {
    background-color: blue;
    width: 100%;
    height: 4rem;
    
}

section {
    background-color: bisque;
    width: 100%;
    display: flex;
    justify-content: space-around;
    }

section article {
    background-color: azure;
    width: 50%; 
    height: 26rem;
    margin: 1rem;
    }

aside {
    background-color: crimson;
    width: 100;
    display: flex;
    justify-content: space-around;     
 }

.ancho65 {
    width: 70%; 
    height: 20rem;
    margin: 1rem
}

.ancho39 {
    width: 30%;
    height: 20rem;
    margin: 1rem
}