y=3x+9

The standard form of a linear equation is Ax+By=C.

Rewrite the equation with the sides flipped.

3x+9=y

Subtract y from both sides of the equation.

3x+9-y=0

Move 9.

3x-y+9=0

3x-y+9=0

Subtract 9 from both sides of the equation.

3x-y=-9

Rewrite in Standard Form y=3x+9