You can either use the usual formula for the equation of a line when given two points [tex](x_1,y_1),\ (x_2,y_2)[/tex]
[tex]\dfrac{x-x_1}{x_2-x_1} = \dfrac{y-y_1}{y_2-y_1}[/tex]
Or we can make some more precise reasoning, specific to this case: the y intercept is 3. When a line is written as [tex]y=mx+q[/tex], the coefficient q is the y intercept. So, the second and third options are surely wrong.
Moreover, the slope m is the ratio between the difference bewteen the y coordinates and the x coordinates of two points on the line.
In our case, the two points differ by -1 units vertically, and 3 units horizontally. This implies that the slope is -1/3.
So, we have
[tex]y=mx+q,\quad m=-\dfrac{1}{3},\quad q=3\implies y=-\dfrac{1}{3}x+3[/tex]
