An unknown element is a mixture of isotopes ¹⁵¹X (atomic mass = 150.99 amu) and ¹⁵³X (atomic mass = 153.03 amu). The average atomic mass of X is 151.36 amu. What is the percent abundance of ¹⁵³X?

You would be correct, boiling water does disinfect contamination.    the property of disinfecting means to kill  germs, bacteria and other pathogens or contamination  that might cause an infection or cause a person to become sickly. a couple methods of disinfecting are using soap, other cleaning supplies or by simply "boiling" the contaminate.  the reason why boiling water disinfects certain attributes is because some cells cannot survive the heat and pressure.