Xiao Fang and Xiao Gang each make 180 parts, and Xiao Fang's production speed is faster than Xiao Gang's (1/5), so when Xiao Fang finishes, how many parts does Xiao Gang still need to make.
小方和小刚每人做180个零件，小方做的速度比小刚快(1/5)，则小方做完时，小刚还需要做多少个．
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 + (1/5)</gadget>
<output>6/5 = around 1.2</output>

<gadget id="calculator">1 / (6/5)</gadget>
<output>5/6 = around 0.833333</output>

<gadget id="calculator">1 - (5/6)</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">180 * (1/6)</gadget>
<output>30</output>

<result>30</result>