.site-header-cart { display:none; }

@media screen and (min-width: 768px) {
    /* LOGO */
    .site-header .site-branding, .site-header .site-logo-anchor, .site-header .site-logo-link { width: 60%  /* Use px values if you want, eg. 350px */ }

    /* SEARCH BAR */
    .site-header .site-search { width: 15%  /* Use px values if you want, eg. 350px */ }
}