Solve inequality:
The measure of the acidity of a liquid is called the pH of a liquid. The pH for a liquid can be described by the formula pH = −log [H+], where [H+] is the concentration of hydrogen ions in moles per liter. Pure water has a pH of 7. Black coffee has a pH of 5. How many times greater is the hydrogen ion concentration of black coffee than that of pure water? Express your answer as a whole number.
