If the product of a and b is both even and prime, and (7/(a))=((b)/(x)), then 7.7x=what.
如果a与b的积既是偶数又是素数，且(7/(a))=((b)/(x))，那么7.7x=多少．
<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">7.7 * (2/7)</gadget>
<output>2.2</output>

<result>2.2</result>