classmate copied 10*(□+3) into 10*□+3 by mistake. How much is the difference between the result he calculated and the correct answer?
一个同学把10*(□+3)错抄成10*□+3，他算出的结果与正确答案相差多少．
<gadget id="calculator">10 * 3</gadget>
<output>30</output>

<gadget id="calculator">30 - 3</gadget>
<output>27</output>

<result>27</result>