Answer: I am assuming that x is the first column and y is the second column.
You are looking for an equation that works with every pair. I.e., when you plug in x, you get the y that is next to it. The only one that works is y = 2.5x.
Explanation:
The first answer is obviously incorrect, because the y values are all larger than the x values, and if you multiply a number by .4, you will get a smaller number, not a larger one.
The second one works for every pair:
2.5(6) = 15, 2.5(8) = 20, 2.5(10) = 25, and 2.5(12) = 30.
The third one works for the first pair of numbers, but only for that one.
The last possibility doesn't work for any of them, and like the first answer, obviously gives a smaller y for each x, so cannot be the right answer.