<?xml version="1.0" encoding="UTF-8"?>
<m:math  xmlns:m="http://www.w3.org/1998/Math/MathML"
     display="block">
     <m:mrow>
         <m:mfenced open="(" close=")"><m:mrow>
                 <m:mn>3</m:mn> 

         </m:mrow>
         </m:mfenced>
     </m:mrow>
</m:math>