15 minus 2 times a number equals 3.4, find this number. (solution by equation)
15减去一个数的2倍等于3.4，求这个数．(用方程解)
<gadget id="calculator">15 - 3.4</gadget>
<output>11.6</output>

<gadget id="calculator">11.6 / 2</gadget>
<output>5.8</output>

<result>5.8</result>