The number of A is 500, the number of B is 780 less than its 5 times, what is the number of B?
甲数是500，乙数比它的5倍少780，乙数是多少？
<gadget id="calculator">500 * 5</gadget>
<output>2_500</output>

<gadget id="calculator">2_500 - 780</gadget>
<output>1_720</output>

<result>1_720</result>