The number of A is 6.5, the number of B is 1.8 less than 3 times of the number of A, what is the number of B?
甲数是6.5，乙数是甲数的3倍少1.8，乙数是多少．
<gadget id="calculator">6.5 * 3</gadget>
<output>19.5</output>

<gadget id="calculator">19.5 - 1.8</gadget>
<output>17.7</output>

<result>17.7</result>