We have a question: The number of math problems that Marvin practiced today is three times as many as the number of problems he solved yesterday. His friend, Arvin, has practiced twice as many math problems on each day. How many math problems have they practiced altogether if Marvin solved 40 math problems yesterday?
And an answer: 480
So how you got the answer?
If Marvin solved 40 math problems yesterday, he has solved 40 * 3 = 120 math problems today. The total number of math problems that Marvin has practiced is 120 + 40 = 160. Arvin has practiced twice as many as Marvin, so has practiced 160 * 2 = 320 problems. Together, Marvin and Arvin have solved 320 + 160 = 480 math problems.

We have a question: Steve's new book sells 1,000,000 copies. He got an advance to pay for 100,000 copies. He gets $2 for each copy of the book sold. His agent takes 10% of that. How much money did he keep not counting the money from the advance?
And an answer: 1620000
So how you got the answer?
He sold 1,000,000 - 100,000 = 900,000 not counting the advance. So he made 900,000 * 2 = $1,800,000 from selling the books. His agent took 1,800,000 * .1 = $180,000. That means he kept 1,800,000 - 180,000 = $1,620,000.

We have a question: James drives 30 mph for half an hour and then twice as long for twice the speed. How far did he drive in total?
And an answer: 75
So how you got the answer?
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.