public static Fraction CreateFraction(IEnumerable <OpenXmlElement> upper, IEnumerable <OpenXmlElement> lower)
{
var fraction = new Fraction();
var numerator = new Numerator();
numerator.Append(upper);
var denominator = new Denominator();
denominator.Append(lower);
fraction.AppendChild(numerator);
fraction.AppendChild(denominator);
return(fraction);
}