A bucket of pure water, after drinking (3/4) there is still 0.5 liters left, and there are 4.5 liters left, how many liters are there in this bucket of pure water?
一桶纯净水，喝掉了它的(3/4)还多0.5升，还剩下4.5升，这桶纯净水共有多少升．
<gadget id="calculator">0.5 + 4.5</gadget>
<output>5</output>

<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">1 - (3/4)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">5 / (1/4)</gadget>
<output>20</output>

<result>20</result>