We need to write an equation that relates x and y.
We know those values vary directly. And one pair of values are given. Thus, we have the following proportion:
values of x values of y
2 5
x y
Then, cross multiplying the above quantities, we obtain:

Now, we need to isolate y on the left side of the equation. We can do so by dividing both sides of the equation by 2. We obtain:

Answer
