Add 0.1 to 4 times a number to get 1.7, find this number.
一个数的4倍再加上0.1得1.7，求这个数．
<gadget id="calculator">1.7 - 0.1</gadget>
<output>1.6</output>

<gadget id="calculator">1.6 / 4</gadget>
<output>0.4</output>

<result>0.4</result>