Answer
Neither of them is exponential.
Work Step by Step
If a function x is an exponential function, then it has form
$f(x)=a\cdot b^{x}$
When we observe an increase of x by 1 unit, $f(x+1)=ab^{x+1}.$
what follows is that the ratio $\displaystyle \frac{f(x+1)}{f(x)}=\frac{ab^{x+1}}{ab^{x}}=b.$
(the ratio is constant when arguments increase by 1).
Thus, if the x increases by unit, the function value is multiplied with b.
We use this to recognize whether a table of function values represent an exponential function or not.
---
The x-values increase by 1 unit.
For the values of f(x) we observe $ \displaystyle \frac{f(x+1)}{f(x)}$:
$\displaystyle \frac{7.5}{2.5}=\frac{1}{3},\quad\frac{2.5}{7.5}=\frac{1}{3},\quad\frac{7.5}{2.5}=3$
so it is not exponential.
For the values of g(x),
$\displaystyle \frac{0.9}{0.3}=3,\quad\frac{2.7}{0.9}=3,\quad\frac{8.1}{2.7}=3,\quad\frac{16.2}{8.1}=2,\quad$
so it is not exponential,
Neither of them is exponential.