is f (x) = 2229 ⋅ 0.9909x an exponential growth or exponential decay function? What is the constant percentage rate of growth or decay?

It is an exponential decay function because f (x) will decrease as x increases, because multiplying by a number less than 1 always decreases somethings value. Each time x increases by 1, you will have 99.09% of what you started with. If I remember my definitions correctly, that means the percentage rate of decay would be 100-99.09 = 0.91%.