Find the value of the coefficient of 1/x in the expansion (2x-1/x)^5

The base of a triangle exceeds the height by 7 centimeters. if the area is 400 square centimeters, find the length of the base and the height of the triangle.

In 2009, there were 1570 bears in a wildlife refuge. in 2010, the population had increased to approximately 1884 bears. if this trend continues and the bear population is increasing exponentially, how many bears will there be in 2018?

Awindow washer cleans 42 windows in 2 hours. at this rate, how many windows did he clean in 180 minutes.