Answer:
y - 3 = (1/2)(x - 1)
Explanation:
As we go from (1, 3) to (5, 1), we see that x (the run) increases by 4 and y (the rise) decreases by 2. Hence, the slope is m = rise / run = 2/4, or m = 1/2.
Then the desired point slope equation is y - 3 = (1/2)(x - 1).