Answer
neither exponential nor linear
Work Step by Step
The ratio of consecutive values is not constant (because $\frac{12}{6}=2\ne\frac{18}{12}=1.5$), hence, it is not an exponential function.
The difference of consecutive values is not constant (because $6-3\ne12-6$), hence it is not a linear function.
Thus, the function is neither linear nor exponential.
