What is the value of the unknown x in the equation 8.1-0.4x=7.98.
方程8.1-0.4x=7.98中未知数x的值为多少．
<gadget id="calculator">8.1 - 7.98</gadget>
<output>0.12</output>

<gadget id="calculator">0.12 / 0.4</gadget>
<output>0.3</output>

<result>0.3</result>