style.css

aside {
    background: white;
}

header {
    padding: 20px;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

div {
    display: flex;
    padding: 10px;
    height: 100%;
}

aside {
    flex-grow: 1;
    min-width: 300px;
    margin-right: 30px;
}

main {
    font-size: 16px;
    line-height: 1.5;
}

img {
    width: 200px;
}