There are ɑ tons of cement on the construction site, and 2.5 tons are used every day. After 6 days of use, how many tons are left?
工地上有ɑ吨水泥，每天用去2.5吨，用了6天后，剩下多少吨．
<gadget id="calculator">2.5 * 6</gadget>
<output>15</output>

<result>15</result>