The boiling point of salt water depends on the percentage of salt. Water with 20 percent salt boils at 216 degrees Fahrenheit, as opposed to 212 degrees Fahrenheit for pure water. Adding a small amount of salt to a pot of boiling water does not make it boil significantly faster.
A pot of water with 20 percent salt boils faster because the salt in the water does not take much of the heat being directed into the solution. Therefore, a pot with high levels of salt is essentially heating up a smaller amount of water than a pot with no salt.