Problem: The World Bank has sponsored a project to curb air pollution through public transport improvements and the Mexican government has started shutting down polluting factories. They have phased out diesel buses and mandated new emission controls on new cars; since 1993 all new cars must be fitted with a catalytic converter, which reduces the emissions released. Trucks must use only liquefied petroleum gas (LPG). Also construction of an underground rail system was begun in 1968 in order to help curb air pollution problems and alleviate traffic congestion. Today it has over 201 km (125 mi) of track and carries over 5 million people every day. Fees are kept low to encourage use of the system and during rush hours the crush is so great, that authorities have reserved a special carriage specifically for women. Due to these initiatives and others, the air quality in Mexico City has begun to improve, with the air becoming cleaner since 1991, when the air quality was declared to be a public health risk for 355 days of the year.[citation needed]
How many people ride the Mexico city subway system each day?
The answer is the following: 5 million people

Problem: The growth continued into the next season, starting with a season premiere of 26.5 million. The season attracted an average of 21.7 million viewers, and was placed second overall amongst the 18–49 age group. The finale night when Ruben Studdard won over Clay Aiken was also the highest-rated ever American Idol episode at 38.1 million for the final hour. By season three, the show had become the top show in the 18–49 demographic a position it has held for all subsequent years up to and including season ten, and its competition stages ranked first in the nationwide overall ratings. By season four, American Idol had become the most watched series amongst all viewers on American TV for the first time, with an average viewership of 26.8 million. The show reached its peak in season five with numbers averaging 30.6 million per episode, and season five remains the highest-rated season of the series.
How many people watched on average for season two?
The answer is the following: 21.7 million

Problem: Qianlong's reign saw the launch of several ambitious cultural projects, including the compilation of the Siku Quanshu, or Complete Repository of the Four Branches of Literature. With a total of over 3,400 books, 79,000 chapters, and 36,304 volumes, the Siku Quanshu is the largest collection of books in Chinese history. Nevertheless, Qianlong used Literary Inquisition to silence opposition. The accusation of individuals began with the emperor's own interpretation of the true meaning of the corresponding words. If the emperor decided these were derogatory or cynical towards the dynasty, persecution would begin. Literary inquisition began with isolated cases at the time of Shunzhi and Kangxi, but became a pattern under Qianlong's rule, during which there were 53 cases of literary persecution.
How many books were in the Siku Quanshu?
The answer is the following: 3,400 books

Problem: Notably, a statute does not disappear automatically merely because it has been found unconstitutional; it must be deleted by a subsequent statute. Many federal and state statutes have remained on the books for decades after they were ruled to be unconstitutional. However, under the principle of stare decisis, no sensible lower court will enforce an unconstitutional statute, and any court that does so will be reversed by the Supreme Court. Conversely, any court that refuses to enforce a constitutional statute (where such constitutionality has been expressly established in prior cases) will risk reversal by the Supreme Court.
What must happen to a statute for it to become unconstitutional?
The answer is the following:
it must be deleted