A can of peanut oil can be eaten by person A in 30 days and person B in 45 days. Two people eat together, how many days to finish?
一罐花生油，甲一人30天吃完，乙一人45天吃完．两人一起吃，几天吃完？
<gadget id="calculator">1 / 30</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">1 / 45</gadget>
<output>1/45 = around 0.022222</output>

<gadget id="calculator">(1/30) + (1/45)</gadget>
<output>1/18 = around 0.055556</output>

<gadget id="calculator">1 / (1/18)</gadget>
<output>18</output>

<result>18</result>