Q: A trolley driver picked up 10 people on his 1st stop. On the next stop, 3 people got off and twice as many people from the 1st stop got on. On the third stop, 18 people got off and 2 got on. How many people are currently on the trolley?
A: Between the trolley driver and his first 10 customers, there are 1 + 10 = 11 people are currently on the trolley. On his first stop, 10 people go on and twice as many people got on at the second stop so 10 * 2 = 20 people got on at the second stop. So at the second stop he had 11 people on board, 3 got off and 20 got on so he now has 11 - 3 + 20 = 28 people. At his third stop 18 people got off and 2 got on so in total there are 28 - 18 + 2 = 12 people on the trolley. The answer is 12.

Q: Johnny is an engineer designing a bridge. The roadway deck for the top of the bridge needs 1600 tons of concrete to construct. The two bridge anchors need equal amounts of concrete, but only one has been built so far, using 700 tons of concrete. Johnny had to calculate how many tons of concrete the supporting pillars underneath the bridge would need, and he found that the total amount of concrete in the entire bridge will be 4800 tons. How much concrete did Johnny find he needs for the supporting pillars?
A: The bridge anchors will take 700 * 2 = 1400 tons of concrete. The roadway deck and bridge anchors need 1600 + 1400 = 3000 tons of concrete. Thus, Johnny found the supporting pillars need 4800 - 3000 = 1800 tons of concrete. The answer is 1800.

Q: James drives 30 mph for half an hour and then twice as long for twice the speed. How far did he drive in total?
A:
His first drive was 30 * .5 = 15 miles. The next leg was .5 * 2 = 1 hour. The speed of the trip was 30 * 2 = 60 mph. So he drove 60 * 1 = 60 miles. So in total he drove 60 + 15 = 75 miles. The answer is 75.