It is known that (4/5)a=(5/4)b, if a=100, then how much is b=.
已知(4/5)a=(5/4)b，如果a=100，那么b=多少．
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(4/5) * 100</gadget>
<output>80</output>

<gadget id="calculator">5 / 4</gadget>
<output>5/4 = around 1.25</output>

<gadget id="calculator">80 / (5/4)</gadget>
<output>64</output>

<result>64</result>