First of all, boiling isn't a chemical reaction. Salt dissolving in water isn't a chemical change.
I don't know how your experiment is done, but salt water is suppose to boil slower than normal water. Do you know salt added to ice melts it? Why? Because it lowers the freezing point of water, so it needs to be more cold to freeze. Salt also makes the boiling point of water higher, so it needs more heat to boil salt water.
Good luck solving that. You know, your conclusions doesn't have to be supported by evidence. What you get is what you get. Just identify the reasons why salt water boiled slower than plain water. Perhaps it's that you didn't regulate the flame, or didn't keep the amount of water the same.
Or you can try to do your experiment again.
God grant me the serenity to accept things I cannot change, the courage to change the things I could, and the wisdom to know the difference.