If the sum of a number and 9 is multiplied by 4 and equals 10000, what is the number?
将一个数与9的和再扩大4倍后等于10000，则这个数是多少．
<gadget id="calculator">10_000 / 4</gadget>
<output>2_500</output>

<gadget id="calculator">2_500 - 9</gadget>
<output>2_491</output>

<result>2_491</result>