Q: In Professor Plum's biology class there are 40 students. Of those students, 80 percent have puppies. Of those who have puppies, 25% also have parrots. How many students have both puppies and parrots?
A: We start with the initial numbers of students, 40 and multiply that by .8 for 40 * 0.8 = 32 who own puppies. That the number of students with puppies, 32, and multiply that by .25 to find out how many own both puppies and parrots, 32 * 0.25 = 8 who own puppies and parrots. The answer is 8. The answer is 8.

Q: Bert fills out the daily crossword puzzle in the newspaper every day. He uses up a pencil to fill out the puzzles every two weeks. On average, it takes him 1050 words to use up a pencil. How many words are in each crossword puzzle on average?
A: At 7 days a week, it takes Bert 2 * 7 = 14 days of daily crossword puzzles to use up a pencil. Since Bert does one puzzle a day, each crossword puzzle has 1050 / 14 = 75 words. The answer is 75.

Q: There are 120 cards in a box. If 2/5 of the cards are red, exactly 5/9 of the remainder are black, and the rest are green, calculate the number of green cards in the box?
A:
The number of red cards in the box, 2 / 5 of the total number, is 2 / 5 * 120 = 48. The number of cards that are not red is 120 - 48 = 72. If 5 / 9 of the remaining cards are black, then there are 5 / 9 * 72 = 40 black cards in the box. If the remaining cards are green, then there are 72 - 40 = 32 green cards in the box. The answer is 32.