A rope, 12m is used for the first time, the rest (3/4) is used for the second time, and exactly 30m is used for the second time. How long is this rope?
一根绳子，第1次用去12m，第2次用去剩下的(3/4)，第2次正好用去30m．这根绳子原来长多少米？
<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">30 / (3/4)</gadget>
<output>40</output>

<gadget id="calculator">40 + 12</gadget>
<output>52</output>

<result>52</result>