Notice that the written functions are mostly incorrectly written, after a short online search i've found the correct ones, which are the ones i will write in this answer.
A general exponential equation can be written as:
f(x) = A*(r)^x
Where A is the initial value, r is the rate of growth, and x is our variable.
If r > 1, the function represents a growth.
if 0 < r < 1, the function represents a decay.
1) f(x) = 3^x
Here we have r = 3
This is clearly larger than 1, then this function represents a growth.
2) f(x) = (0.25)^x
Here we have r = 0.25, which is smaller than 1 and larger than zero, then this function represents a decay.
3) f(x) = (2/3)^x
here we have r = 2/3 = 0.66
This is larger than zero and smaller than 1, then this function represents a decay.
4) f(x) = (3/2)^x
Here we have r = 3/2 = 1.5
This is larger than 1, then this function represents a growth,