Explanation:
the slope is the y/x ratio of the y and x coordinate differences when going from one point to the other. and it is always the factor of x in the equation.
x changes by 4 units (from 0 to 4), y changes by -1 unit (from 3 to 2).
so, the slope is -1/4.
the intercept means the intercept with the y-axis. and that means the y value when x = 0. which is given already by the first point : 3
so, the equation is
y = -1/4 x + 3