At first glance, one would think this problem isn't possible. But if you use the magnifying glass, you see that it is.
Solve
25 carrots puts you somewhere to the left of the shaded area, so C and D are both wrong.
That leaves you with A or B. You need 30 carrots (or just very slightly less) at least to solve this problem. The way to distinguish between A and B is to look at the line that goes from lower right to upper left. When you magnify this graph, you see that at 30 carrots the line or boundary goes through 20 cucumbers. 21 is just very slightly above that and 25 is far above the other line. 21 cucumbers is the only possible right answer for the number of cucumbers. 25 is too high. B is wrong. The answer is A.
