The graph of function g(x) = -3x + 2 has a y-intercept of (0, 2) and a slope of -3. I highly recommend drawing this straight line using this info.
You can read the value of f(0) directly from the graph; it is 0. Subst. 0 for x in g(x) = -3 + 2 results in g(0)=2, which is greater than f(0) = 0.
Now compare f(2) and g(2):
From the graph, f(2) = 4. From g(x) = -3x + 2, g(2) = -4. Obviously f(2) is greater than g(2) here.
Next, compare f(-1) and g(-1). From the graph, f(-1) = -4. From g(x) = -3x + 2, we see that g(-1) = 5. So, f(-1) is less than g(-1).