.section-responsive_full_width_image img {
    width: 100%;
    height: auto;
}

.section-responsive_full_width_image img.mobile {
    display: none;
}

@media screen and (max-width: 599px) {
    .section-responsive_full_width_image img.mobile {
        display: block;
    }
    
    .section-responsive_full_width_image img.desktop {
        display: none;
    }
}