can someone help me with standard form?

Standard Form: Ax + By = C
So I normally use the y intercept to find the standard since it's easier.
[tex]y = 3x + 9[/tex]
First subtract 3x from both sides.
[tex]-3x + y = 9[/tex]
You can leave the equation like this but I like taking out the negatives from the beginning variable. Divide both sides by negative one.
[tex]3x - y = -9[/tex]
That should be your answer now.