A passenger ship departs from Port A. On the way to Port B, there are (2/7) passengers disembarking and 45 people boarding. At this time, the number of passengers on board is equivalent to (20/21) when departing from Port A. , Ask: How many passengers are there at this time?
一艘客轮从甲港开出，途中到乙港有(2/7)的乘客离船，又有45人上船，这时船上乘客人数相当于从甲港开出时的(20/21)，问：这时有多少乘客？
<gadget id="calculator">20 / 21</gadget>
<output>20/21 = around 0.952381</output>

<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">1 - (2/7)</gadget>
<output>5/7 = around 0.714286</output>

<gadget id="calculator">(20/21) - (5/7)</gadget>
<output>5/21 = around 0.238095</output>

<gadget id="calculator">45 / (5/21)</gadget>
<output>189</output>

<gadget id="calculator">189 * (20/21)</gadget>
<output>180</output>

<result>180</result>