Subtract the product of 1.3 and 8 from 3 times a number to get 1.9. Find this number.
一个数的3倍减去1.3与8的积，得1.9，求这个数．
<gadget id="calculator">1.3 * 8</gadget>
<output>10.4</output>

<gadget id="calculator">1.9 + 10.4</gadget>
<output>12.3</output>

<gadget id="calculator">12.3 / 3</gadget>
<output>4.1</output>

<result>4.1</result>