Q: Martin has 18 goldfish. Each week 5 goldfish die. Martin purchases 3 new goldfish every week. How many goldfish will Martin have in 7 weeks?
A: In 7 weeks 5 * 7 = 35 goldfish die. In 7 weeks, Martin purchases 3 * 7 = 21 goldfish. In 7 weeks, Martin will have 18 - 35 + 21 = 4 goldfish. The answer is 4.

Q: Rafael works 10 hours on Monday and 8 hours on Tuesday on his delivery job. With 20 hours left to work in the week, how much money does Rafael make if he is paid $20 per hour?
A: The total number of hours that Rafael has worked by Tuesday is 8 + 10 = 18 hours. To complete his assigned work hours, Rafael works 20 hours more, making his total weekly hours to be 18 + 20 = 38 hours. Since he is paid $20 per hour, he makes $20 * 38 = $760 a week. The answer is 760.

Q: Max likes to collect model trains. He asks for one for every birthday of his, and asks for two each Christmas. Max always gets the gifts he asks for, and asks for these same gifts every year for 5 years. At the end of the 5 years, his parents give him double the number of trains he already has. How many trains does Max have now?
A:
Max gets 1 + 2 = 3 trains per year. He repeats this for 5 years, meaning he gets 5 * 3 = 15 trains. When this number is doubled by his parents, it becomes 15 * 2 = 30 trains. Since he already had 15 model trains, his total becomes 15 + 30 = 45 trains. The answer is 45.