Question: Prejean's speed in a race was three-quarters that of Rickey. If they both took a total of 70 minutes to run the race, calculate the total number of minutes that Rickey took to finish the race.
Answer with step-by-step thinking: Let's say Rickey took t minutes to finish the race. If Prejean's speed in the race was three - quarters that of Rickey, and Rickey took t minutes to finish the race, the time that Prejean took to finish the race is 3 / 4 * t = 3 / 4t. Together, Rickey and Prejean took t + 3 / 4t = 70. They took 1 3 / 4 t hours = 70 to finish the race. This is 7 / 4t = 70. t = 70 * 4 / 7. The time that Rickey took to finish the race is t = 40 minutes.
So the answer is 40.

Question: Tyler has 21 CDs. He gives away a third of his CDs to his friend. Then he goes to the music store and buys 8 brand new CDs. How many CDs does Tyler have now?
Answer with step-by-step thinking: Tyler gives away 21 / 3 = 7 CDs. After giving away a third of his CDs, Tyler has 21 - 7 = 14 CDs. After buying new CDs, Tyler has 14 + 8 = 22 CDs.
So the answer is 22.

Question: Bill is trying to control the pests in his garden. Each spider he introduces eats 7 bugs, and each time he sprays the garden he reduces the total bug population to 80% of what it was previously. If the garden has 400 bugs to start, and Bill sprays once and introduces 12 spiders, how many bugs are left?
Answer with step-by-step thinking:
First find the total bug population after spraying: 80% * 400 bugs = 320 bugs. Then find the total number of bugs each spider eats: 12 spiders * 7 bugs / spider = 84 bugs. Then subtract that number from the number of bugs left after spraying to find final number of bugs: 320 bugs - 84 bugs = 236 bugs.
So the answer is 236.