Obviously, when doing addition, the 6 in the tens place of an addend is regarded as 9, and the ones digit 9 is regarded as 7, and the resulting sum is 201. What should be the correct result.
明明做加法时，把一个加数的十位上的6看作9，把个位数字9看作7，结果所求的和为201．正确的结果应该是多少．
<gadget id="calculator">90 - 60</gadget>
<output>30</output>

<gadget id="calculator">201 - 30</gadget>
<output>171</output>

<gadget id="calculator">9 - 7</gadget>
<output>2</output>

<gadget id="calculator">171 + 2</gadget>
<output>173</output>

<result>173</result>