It would be A.
I used to get stuck on these too. So the equations are mostly used for things like charts, so I would make a chart and it would help me a lot.
Okay, so the equation for a, y = 3x + 3
Remember that x and y in the equation, are referring to the x and y points on the graph.
So, the line intercepts first at (1,6) 1 is x, 6 is y. Now use those in the equation,
y= 3x + 3 and plug in the numbers, 6 = 3 * 1 + 3
3 * 1 = 3
3+3 = 6 (y)
So far the equation is true.
Now, the line intercepts next at (2,9), 2 is x, 9 is y.
Do the same with the equation, y= 3x + 3
9 = 3 * 2 + 3
3 *2 = 6
6+3 = 9.
This is true.
Next, the line intercepts at (3, 12), 3 is x, 12 is y.
Now use the equation, y= 3*x + 3.
12 = 3 * 3 + 3
3 * 3 = 9
9 + 3 = 12.
This is true.
Next, the line intercepts at (4, 15), 4 is x, y is 15.
Use the equation y = 3x + 3
15 = 3 * 4 + 3
3 * 4 = 12
12 + 3 = 15.
This is true.
And finally, the line intercepts at (5, 18), 5 is x, 18 is y.
Use the equation y= 3x + 3.
18 = 3 * 5 + 3
3 * 5 = 15
15 + 3 = 18.
This is true.
So your Answer is A. y = 3x + 3.