Answer:
I'm pretty sure it's 4 sorry if I'm not right I'm not the best at this stuff either
The answer is D. The +1 refers to the extra cup leftover from a previous bag. X represents how many cups are in each bag, and that is what you need to know. The three represents how many bags she bought, and the 25 represents how many cups of birdseed she had overall.
Hopefully this helps!