The construction site needs to mix 30 tons of cement, 7 trucks have been mixed, and another 2 tons will be mixed. How many tons of concrete are mixed on average per truck?
建筑工地需要拌制30吨水泥，已经拌制了7车，还要再拌制2吨，平均每车拌制多少吨混凝土？
<gadget id="calculator">30 - 2</gadget>
<output>28</output>

<gadget id="calculator">28 / 7</gadget>
<output>4</output>

<result>4</result>