master
<math><mrow><msub><mi>P</mi><mi>x</mi></msub><mo>=</mo><mi>P</mi><mo>−</mo><mspace width="0.167em" /><mrow><mi>a</mi><mo>∣</mo><mi>a</mi><mo>≥</mo><mi>x</mi><mspace width="0.167em" /></mrow></mrow></math>