The sloppy Xiaogang copied 10*(a+2) into 10*a+2. Think about it, how much is the difference between his calculated result and the correct answer?
马虎的小刚把10*(a+2)抄成了10*a+2，想一想，他算出的结果与正确答案相差多少？
<gadget id="calculator">10 * 2</gadget>
<output>20</output>

<gadget id="calculator">20 - 2</gadget>
<output>18</output>

<result>18</result>