mml=<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#x2234;</mo><mi mathvariant="normal">&#xA0;</mi><mn>28</mn><mi mathvariant="normal">%</mi><mo>=</mo><mfenced open="[" close="]" separators="|"><mrow><mo>-</mo><mn>20</mn><mo>+</mo><mi mathvariant="normal">x</mi><mo>+</mo><mfrac><mrow><mfenced separators="|"><mrow><mo>-</mo><mn>20</mn></mrow></mfenced><mo>&#xD7;</mo><mi mathvariant="normal">x</mi></mrow><mn>100</mn></mfrac></mrow></mfenced><mi mathvariant="normal">%</mi><mspace linebreak="newline"/><mn>28</mn><mo>+</mo><mn>20</mn><mo>=</mo><mfenced open="[" close="]" separators="|"><mrow><mi mathvariant="normal">x</mi><mo>-</mo><mfrac><mrow><mn>20</mn><mi mathvariant="normal">x</mi></mrow><mn>100</mn></mfrac></mrow></mfenced><mi mathvariant="normal">%</mi><mo>&#x21D2;</mo><mn>48</mn><mo>=</mo><mfenced open="[" close="]" separators="|"><mfrac><mrow><mn>100</mn><mi mathvariant="normal">x</mi><mo>-</mo><mn>20</mn><mi mathvariant="normal">x</mi></mrow><mn>100</mn></mfrac></mfenced><mi mathvariant="normal">%</mi><mspace linebreak="newline"/><mo>&#x2234;</mo><mi mathvariant="normal">&#xA0;</mi><mn>80</mn><mi mathvariant="normal">x</mi><mo>=</mo><mn>4800</mn><mo>&#x21D2;</mo><mi mathvariant="normal">x</mi><mo>=</mo><mfrac><mn>4800</mn><mn>80</mn></mfrac><mo>=</mo><mn>60</mn><mi mathvariant="normal">%</mi></math>