Answer
f(x) = -12x+100
Work Step by Step
1. Remember we are writing the function in the form f(x) = ax+b.
2. Since a = rate of change and rate of change in this case = -12, we have f(x) = 12x+b.
3. Since the initial value is when x = 0 (the y-intercept), which = b, we know that b = 100
4. We now have f(x) = -12x+100