Add 4 to a number, subtract 3, multiply by 5 and divide by 6 to get 15. What is the number?
一个数加上4，减去3，乘5再除以6得15，这个数是多少．
<gadget id="calculator">6 / 5</gadget>
<output>6/5 = around 1.2</output>

<gadget id="calculator">15 * (6/5)</gadget>
<output>18</output>

<gadget id="calculator">3 - 4</gadget>
<output>-1</output>

<gadget id="calculator">18 + (-1)</gadget>
<output>17</output>

<result>17</result>