Hope this helps! I'm sorry for worse handwriting.
Step-by-step explanation:
if f (x) = 100 - x;
as x increases, the value of f(x) will decrease
If you are working with time or days, you can't put in a negative value because if you are doing an experiment, you can't go back in time to do that experiment to gather data. (Time for the most part considered to be an input value so that's why I used it as an example.)
