<?xml version="1.0" encoding="UTF-8"?>
<math xmlns="http://www.w3.org/1998/Math/MathML">
<msub>
<mi>P</mi>
<mi>x</mi>
</msub>
<mo>=</mo>
<mi>P</mi>
<mo>-</mo>
<mfenced close="}" open="{">
<mrow>
<mi>a</mi>
<mo>∣</mo>
<mi>a</mi>
<mo>≥</mo>
<mi>x</mi>
</mrow>
</mfenced>
</math>