Two lines are parallel. the equation of the first line is y = –3x + 5. which of the following cannot be the equation of the second line?

It sounds like you were given a list of choices. That list is missing. Without the list, it's impossible to say which is the answer; however, I can help you narrow things down.

The slope of y = -3x+5 is -3. It's the value just to the left of the x. Any line parallel to this line will also have a slope of -3. Parallel lines have equal slopes.

So I'm assuming your list of choices have various equations with slopes of -3. The only oddball will have some other slope, and that will be the answer. If it has some other slope, then the line won't be parallel to y = -3x+5 and will cross that line somewhere. 



Edit: Thank you for posting those choices

The answer is choice B since it's the only graph that has a slope of something other than -3. In this case, the graph B has a slope of 1/3. You get this by solving each equation for y. So x-3y = -3 would turn into y = (1/3)x + 1