A project can be completed in 25 days by A alone, and 20 days by B alone. After 3 days of joint work, how much of the project is left?
一项工程，甲单独做要25天完成，乙单独做要20天完成，两人合做3天后，还剩下这项工程的多少．
<gadget id="calculator">1 / 25</gadget>
<output>1/25 = around 0.04</output>

<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(1/25) + (1/20)</gadget>
<output>9/100 = around 0.09</output>

<gadget id="calculator">(9/100) * 3</gadget>
<output>27/100 = around 0.27</output>

<gadget id="calculator">1 - (27/100)</gadget>
<output>73/100 = around 0.73</output>

<result>73/100 = around 0.73</result>