A construction site uses trucks to transport soil, and each vehicle transports a ton. 4 trucks were shipped in the morning, and 3 trucks were shipped in the afternoon. How many tons were shipped in total on this day?
一个工地用汽车运土，每辆车运a吨．上午运了4车，下午运了3车，这一天一共运了多少吨．
<result>7</result>