Jason is counting the number of cars that drive by his window. He counted four times as many green cars as red cars, and 6 more red cars than purple cars. If he counted 312 cars total, how many of them were purple? Give the rationale and then the answer.
Let's think step by step. Let g be the number of green cars, r be the number of red cars, and p be the number of purple cars. We know that g + r + p = 315, r = p + 6, and g = 4r. Substitute the second equation into the third equation to get: g = 4r = 4(p + 6) = 4p + 24. Now substitute the equations that express g and r in terms of p in the equation for the total number of cars: 4p + 24 + p + 6 + p = 315. Now combine like terms to get 6p + 30 = 312. Now subtract 30 from both sides to get 6p = 282. Now divide both sides by 6 to get p = 47.. The answer is: 47.

Karen is packing her backpack for a long-distance hike. She packs 20 pounds of water, 10 pounds of food, and 20 pounds of gear. During her hike, she drinks 2 pounds of water per hour and eats 1/3rd the weight of food per hour as water per hour. How much weight is she carrying after six hours? Give the rationale and then the answer.
Let's think step by step. First find the weight of food Karen eats every hour: 2 pounds * 1 / 3 = 2 / 3 pounds food. Then find the total amount of weight Karen's backpack loses per hour she hikes: 2 pounds water / hour + 2 / 3 pound food / hour = 8 / 3 pounds / hour. Multiply this by the number of hours she hikes to find the total amount of weight she loses: 8 / 3 pounds / hour * 6 hours = 16 pounds. Add the weight of all her items to find total starting weight: 20 pounds + 10 pounds + 20 pounds = 50 pounds. Then subtract the weight she loses from the starting weight to find the weight after 6 hours: 50 pounds - 16 pounds = 34 pounds.. The answer is: 34.

Josie received $50 as a gift. She plans to buy two cassette tapes that cost $9 each and a headphone set that costs $25. How much money will she have left? Give the rationale and then the answer.
Let's think step by step. The cassette tapes will cost 2 × 9 = $18. She spends 18 + 25 = $43 in total. Josie will have 50 - 43 = $7 left.. The answer is: 7.