How many milliliters are left after pouring out 750 milliliters of 2 liters of water?
2升水倒出750毫升后，还剩多少毫升．
<gadget id="calculator">2 * 1_000</gadget>
<output>2_000</output>

<gadget id="calculator">2_000 - 750</gadget>
<output>1_250</output>

<result>1_250</result>