@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;

}