sass mixin for rem font sizing & line height with px fallback

@mixin font-size($sizeValue: 16, $line: $sizeValue * 1.5) {
    font-size: ($sizeValue) + px;
    line-height: ($line) + px;
    font-size: ($sizeValue / 16) + rem;
    line-height: ($line / 16) + rem;
}