How do i find if x and y are direct variables in a problem like this: y-9=6+x?

First thing is to group the equation according to likeness
 In an "equation", both sides must be equal.
y-9 = 6+x
1. Group according to likeness;
 x and y should be on the same side of the equation and 9 and 6 should be on the same of the equation.
2. The equation then becomes
y= 6+ x - 9
y=-3+x

x = y - 3
y = 3 + x
x-y= 3

y = 3 + y - 3
y-3 =  y-3

The sides are =