In the formula 251*口/3*8-10=1998, what number should be filled in the mouth.
在算式251*口/3*8-10=1998中，口内应填入的数字是多少．
<gadget id="calculator">251 * 3</gadget>
<output>753</output>

<gadget id="calculator">753 / 251</gadget>
<output>3</output>

<result>3</result>