span.frac {
    display: inline-block;
    text-align: center;
    vertical-align: middle;
    }
    span.frac > sup, span.frac > sub {
    display: block;
    font: inherit;
    padding: 0 0.3em;
    }
    span.frac > sup {border-bottom: 0.08em solid;}
    span.frac > span {display: none;}