Due to his carelessness, the little sloppy miscalculated 30*(□+3) as 30*□+3, so how much difference between the result he got and the correct result.
小马虎由于粗心大意，把30*(□+3)错算成了，30*□+3，那么，他得到的结果与正确的结果相差多少．
<gadget id="calculator">30 * 3</gadget>
<output>90</output>

<gadget id="calculator">90 - 3</gadget>
<output>87</output>

<result>87</result>