The number of A is 8.4, which is 0.8 less than 4 times of the number of B. What is the number of B?
甲数是8.4，比乙数的4倍少0.8，乙数是多少
<gadget id="calculator">8.4 + 0.8</gadget>
<output>9.2</output>

<gadget id="calculator">9.2 / 4</gadget>
<output>2.3</output>

<result>2.3</result>