A piece of cloth first uses up one-third of its total length, then uses up the remaining three-quarters, and finally leaves 20 centimeters. How many centimeters is this piece of cloth originally?
一块布先用去全长的三分之一，又用去余下的四分之三，最后余下20公分，这块布原来是多少公分？
<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">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 - (1/3)</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">20 / (1/4) / (2/3)</gadget>
<output>120</output>

<result>120</result>