Article: According to conservation of energy, energy can neither be created (produced) nor destroyed by itself. It can only be transformed. The total inflow of energy into a system must equal the total outflow of energy from the system, plus the change in the energy contained within the system. Energy is subject to a strict global conservation law; that is, whenever one measures (or calculates) the total energy of a system of particles whose interactions do not depend explicitly on time, it is found that the total energy of the system always remains constant.

Question: The total inflow of energy into a system must equal what?
Ans: total outflow of energy from the system, plus the change in the energy contained within the system

Article: Having sold more than 300 million records worldwide, Madonna is recognized as the best-selling female recording artist of all time by Guinness World Records. The Recording Industry Association of America (RIAA) listed her as the best-selling female rock artist of the 20th century and the second best-selling female artist in the United States, with 64.5 million certified albums. According to Billboard, Madonna is the highest-grossing solo touring artist of all time, earning US $1.31 billion from her concerts since 1990. She was ranked at number two, behind only The Beatles, on the Billboard Hot 100 All-Time Top Artists, making her the most successful solo artist in the history of American singles chart. Madonna became one of the five founding members of the UK Music Hall of Fame and was inducted into the Rock and Roll Hall of Fame in her first year of eligibility.

Question: Since 1990, how much did Madonna make in her concerts?
Ans: $1.31 billion

Article: Due to many centuries of intensive settlement, most of the area is shaped by human influence. The original natural vegetation of Thuringia is forest with beech as its predominant species, as can still be found in the Hainich mountains today. In the uplands, a mixture of beech and spruce would be natural. However, most of the plains have been cleared and are in intensive agricultural use while most of the forests are planted with spruce and pine. Since 1990, Thuringia's forests have been managed aiming for a more natural and tough vegetation more resilient to climate change as well as diseases and vermin. In comparison to the forest, agriculture is still quite conventional and dominated by large structures and monocultures. Problems here are caused especially by increasingly prolonged dry periods during the summer months.

Question: What has been the aim for the Thuringian forests since 1990?
Ans: more natural and tough vegetation

Article: Of the 10 most populous U.S. cities, Houston has the most total area of parks and green space, 56,405 acres (228 km2). The city also has over 200 additional green spacestotaling over 19,600 acres (79 km2) that are managed by the cityincluding the Houston Arboretum and Nature Center. The Lee and Joe Jamail Skatepark is a public skatepark owned and operated by the city of Houston, and is one of the largest skateparks in Texas consisting of 30,000 (2,800 m2) square foot in-ground facility. The Gerald D. Hines Waterwall Parklocated in the Uptown District of the cityserves as a popular tourist attraction, weddings, and various celebrations. A 2011 study by Walk Score ranked Houston the 23rd most walkable of the 50 largest cities in the United States. Wet'n'Wild SplashTown is a water park located north of Houston.

Question: How many acres of land does Houston's green spaces cover?
Ans:
19,600