Hello there! It is the second line, line X.
The equation asks which line is represented by the given equation, f(x)=3x+5. Well, since the equation is in y-intercept form, y = mx + b, we know m is the slope, so the slope is 3, and b is the y intercept, so they intercept is 5.
If any of the lines on the graph intersect at (0,5), or through the y axis at 5, they have a y intercept of 5 and could potentially be the correct answer. There is only one lune that does this, line x, making this the answer.
I hope this was helpful and have a great rest of your day!