The population of a small town increased by 25% two years ago and then decreased by by 25% last year. The population is now 4500 persons. What was the population before the two changes?
9,000. It decreased by 50% (25%+25%) over three years, which in this case won't matter, because of the question. If 4,500 is 50% of x then just multiply 4,500 by two.
