From top to bottom:
1) Linear
2) Quadratic
3) Exponential
1) Examining the tables, let's begin by focusing on the y-column:
As we can see the difference from each output is the same, namely: -3
So, we can tell this is a Linear Equation.
2) In this one, let's start out counting the first difference. Note that the 1st difference is not constant. Now, let's do the second difference that yields a constant result:
Since the 2nd difference is the same then we can tell that this is a Quadratic function.
3) Finally, let's examine the last table (from top to bottom):
Focusing on the y-values column we can see a ratio of 2 between each value. Each value is twice the preceding one.
So, this is an exponential function.