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

.contenedor{max-width: 75rem; margin:auto;}

header{ width: 100%; background: #6ab245; height: 10rem}
main{display:flex}
section{width:65%; background: #2ac5ff; display: flex;}
section article{width:30%; background: orange; height: 15rem; margin: 1rem 1rem 1rem 1rem; }

aside { width: 35%; background: #c9c8c8}

footer {width: 100%; background: #6ab245; height: 7rem}