We can write an exponential function as:

The value that determines if it corresponds to growth or decay is the coefficient "b": if b is less than 1, the function represents an exponential decay, and if it is bigger than 1 it represents an exponential gorwth.
In this case, f(x) = 3 * (3/4)^x, the value of b is b=3/4 and it is less than 1, so it represents an exponential decay:
Answer: Exponential decay