mpadded17

W3C sample	WIRIS
	$x+y+z+N+M=a+b+c$

<math xmlns="http://www.w3.org/1998/Math/MathML">
  <mi>x</mi>
  <mo>+</mo>
  <mi>y</mi>
  <mo>+</mo>
  <mi>z</mi>
  <mo>+</mo>
  <mstyle mathbackground="yellow">
    <mpadded width="-3em">
      <mi>N</mi>
      <mo>+</mo>
      <mi>M</mi>
    </mpadded>
  </mstyle>
  <mo>=</mo>
  <mi>a</mi>
  <mo>+</mo>
  <mi>b</mi>
  <mo>+</mo>
  <mi>c</mi>
</math>

Author: Design Science, Inc. (D. Doyle, E. Cannon, E. Tabacman, R.Miner)