There is a batch of cement on the construction site, 15 tons were transported away, and the rest (1/5) was transported away. How many tons of cement were there on the construction site?
工地上有一批水泥，运走了15吨，余下的是运走的(1/5)，工地上原有水泥多少吨？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">15 * (1/5)</gadget>
<output>3</output>

<gadget id="calculator">15 + 3</gadget>
<output>18</output>

<result>18</result>