from (1), which thus tells us that x is positive. the answer must be a or d. the cube of a positive number is positive; the cube of a negative number is negative, and so (2) tells us that x is positive. and so the answer is d.
13. a certain straight corridor has four doors, a, b, c and d (in that order) leading off from the same side. how far apart are doors b and c? 1. the distance between doors b and d is 10 meters. 2. the distance between a and c is 12 meters.
it is obvious that neither (1) or (2) alone can tell you how 