15. There is a number that first subtracts 5, then divides by 2, then adds 3, and finally multiplies by 3. The result is 27. What is this number?
15．有一个数先减去5，再除以2，然后加上3，最后乘3，结果等于27，这个数是多少．
<gadget id="calculator">27 / 3</gadget>
<output>9</output>

<gadget id="calculator">9 - 3</gadget>
<output>6</output>

<gadget id="calculator">6 * 2</gadget>
<output>12</output>

<gadget id="calculator">12 + 5</gadget>
<output>17</output>

<result>17</result>