@media (-o-min-device-pixel-ratio: 2/1) {
  .test-math-and-units {
    font: ignores 0/0 rules;
    test-division: 4 / 2 + 5em;
    simple: 1px + 1px;
  }
}
#units {
  t1: (2em/1em) + 20;
  t2: 20 + (2em/1em);
  t3: 2em/1em;
  t4: (2em/1px) + 20;
  t5: 20 + (2em/1px);
  t6: 2em/1px;
  t7: (2em*1em) + 20;
  t8: 20 + (2em*1em);
  t9: 2em*1em;
  t10: (2em*1px) + 20;
  t11: 20 + (2em*1px);
  t12: 2em*1px;
}