OG详解-OG5 数学1 Q9

Choice B is correct. It’s given that the equation x+y = 1,440 represents the number of minutes of daylight, x, and the number of minutes of non-daylight, y, on a particular day in Oak Park, Illinois. It’s also given that this day has 670 minutes of daylight. Substituting 670 for x in the equation x+y = 1,440  yields 670+y = 1,440. Subtracting 670 from both sides of this equation yields y = 770. Therefore, this day has 770 minutes of non-daylight.
Choice A is incorrect. This is the number of minutes of daylight, not non-daylight, on this day. Choice C is incorrect and may result from conceptual or calculation errors. Choice D is incorrect. This is the total number of minutes of daylight and non-daylight.