When dealing with algebraic equations, I imagine a teeter-totter on a playground. To make both sides stay equal, what you do to one side, do to the other side too.
You know that the "y" value has to be on the left side and everything else on the right side of the equal sign. Start by getting the "x" value to the right by subtracting on both sides. Now you have 3y=-x+3.
You are so close to being done. You just have to get the Y by itself. If the left side has 3y that is a multiplication holding those pieces together. The opposite is dividing. Dividing 3y by 3 will get y by itself. Make sure to do it to both sides of the equation.
Now y=-1/3x+1.
You get this on the left side by -x/3 (which equals -1/3 x and is a negative slope falling from left to right.)and 3/3=1
m=-1/3x and b=1 at the point (0,1)