Answer:
First at all, you need to remember that y-intercept is the point where the line crosses the y-axis. In other words you need to have X=0, so your point is X=0 and Y=-3.
Second, you have the value of the slope which is 2/3.
With this information you can use the lineal equation in slope of a line form : m=(Y2 - Y1) / (X2 - X1)
Substitute the values of your point (0, -3) and the value of the slope 2/3, and rewrite the equation:
Y - (-3) / (X - 0) = 2/3
(Y + 3) / X = 2/3
Multiplying both sides of the equation by X
Y + 3 = (2/3)X, subtracting -3 in both sides of the equation you are going to have your equation base on the value of the slope and y-intercept
Y= (2/3)X - 3