This question involves minimal work. We just need to convert from standard form to slope-intercept form and look for identical equations.
Let’s start by moving the x term to the other side....
6x + 3y = 9
3y = -6x + 9
Now divide by 3 to isolate the y-value....
3y = -6x + 9
y = -2x + 3
Now this should be your final answer, but since your options do not contain the correct answer in slope-intercept form, we can convert it back to standard form to get our final answer. [note: all this work could have been avoided if we noticed that the equation from the problem was divisible by 3, but this is good practice for converting between forms; I promise it will help in future math classes]
y = -2x + 3
Subtract the x term from both sides....
y + 2x = 3
And there you have it! Your final answer is option A, y + 2x = 3