First you need to identify whether the function is linear or exponential. Since the graph is a straight line, the function is a linear function. The graph of an exponential function is a curved one.
Next you need to identify if the graph is increasing or decreasing. By observing the graph we can tell that it is falling from left towards right i.e. as the values of x increase the values of y decreases. This means the graph is decreasing.
Hence the answer to this question is Linear decreasing.