The number of original long skipping ropes in a school accounts for (3/8) of the total number of long and short skipping ropes. Later, another 20 long skipping ropes were bought. At this time, the number of long skipping ropes accounted for (7/12) of the total number of long and short skipping ropes. How many long and short skipping ropes are there in this school?
某学校原有长跳绳的根数占长、短跳绳总数的(3/8)．后来又买进20根长跳绳，这时长跳绳的根数占长、短跳绳总数的(7/12)，这个学校现有长短跳绳的总数是多少根？
<gadget id="calculator">12 - 7</gadget>
<output>5</output>

<gadget id="calculator">7 / 5</gadget>
<output>7/5 = around 1.4</output>

<gadget id="calculator">8 - 3</gadget>
<output>5</output>

<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">(7/5) - (3/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">7 / 12</gadget>
<output>7/12 = around 0.583333</output>

<gadget id="calculator">1 - (7/12)</gadget>
<output>5/12 = around 0.416667</output>

<gadget id="calculator">20 / (4/5) / (5/12)</gadget>
<output>60</output>

<result>60</result>