Question 316303
You want to do the same thing to both sides of the equation. For instance, we can subtract 4x from both sides. 

{{{ 3y = 4x + 9}}}. Subtract 4x from both sides. Now we have 

{{{ 3y - 4x  = 9}}}, which is answer choice d or b. These two are really the same answer because {{{3y-4x = -4x + 3y}}} by the commutative property. The answer is NOT c however.