A's (4/5) is equal to B's (1/5), and B's number is 120. What is A's number?
甲数的(4/5)和乙的(1/5)相等，乙数是120，甲数是多少．
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(1/5) / (4/5)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">120 * (1/4)</gadget>
<output>30</output>

<result>30</result>