If ((a)/(b))=((c)/(d))(b≠0, d≠0), then ad=how much; if 5a=4b, then ((())/(() ))=((())/(())).
如果((a)/(b))=((c)/(d))(b≠0，d≠0)，那么ad=多少；如果5a=4b，那么((())/(()))=((())/(()))．
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<result>4/5 = around 0.8</result>