Given,
Population of city on last day of year 1998 = 72000
Increasing rate in 1999 = 7%
Decreasing rate in 2000 = 10 %
So,
Population at the end of 2000 \(= 72000\times({1}+\frac{7}{100})({1}-\frac{10}{100})\)
\(= 72000\times\frac{107}{100}\times\frac{9}{10}\) = 69336.