Slope-intercept form is y=mx+b, with m being the slope and b being the y-intercept.
y-intercept is the point where the graph intersects ith the y-axis. From the graph, you know it is 4.
The slope is the change in y/change in x. Choose two random points. I chose (-3,0) and (0,4).
(0-4)/(-3-0)=-4/-3=4/3
The slope is 4/3.
Putting it into the equation, the equation of the line is y=4/3x+4
Hope this helps!