The supermarket ships 40 tons of rice and sells 3.5 tons every day. How many tons are left after selling for a day?
超市运来40吨大米，每天卖3.5吨，卖了a天后还剩多少吨．
<gadget id="calculator">40 - 3.5</gadget>
<output>36.5</output>

<result>36.5</result>