In the "Water Conservation" activity in the community, Lingling's household used 15 tons of water, saving 3 tons compared with last month. How many kilograms of water did Lingling's household use last month?
在小区"节约用水"活动中，玲玲家用水15吨，比上个月节约了3吨，玲玲家上个月用水多少千克？
<gadget id="calculator">15 - 3</gadget>
<output>12</output>

<gadget id="calculator">12 * 1_000</gadget>
<output>12_000</output>

<result>12_000</result>