The teacher wants to make 100 number cards from 1 to 100. When printing, the printer malfunctioned and the number "1" was mistakenly typed into "7", so how many number cards were wrongly typed.
老师要制作1-100这100张数卡，在打印时，打印机发生了故障，将数字"1"错打成了"7"，那么有多少张数卡被打错了．
<gadget id="calculator">1 - 1</gadget>
<output>0</output>

<gadget id="calculator">10 + 10 + 0</gadget>
<output>20</output>

<result>20</result>