<RichTextBox xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation">
    <FlowDocument>
        <Paragraph>
            <Run Foreground="Blue" FontSize="15" FontWeight="Bold">Prezent</Run>
            <Run>dla</Run>
            <Bold Foreground="Red" FontSize="20">DZIEWCZYNY</Bold>
        </Paragraph>
    </FlowDocument>
</RichTextBox>

