Why the book asks this here. In the mountain-range infographic, Everest appears to be about twice as tall as Elbrus. Check that with the real numbers:
Height of Elbrus = 5642 m
Twice Elbrus = 5642 × 2 = 11 284 m
Height of Everest = 8848 m
8848 < 11 284 — so Everest is not twice as tall as Elbrus ✘
Everest is in fact about 1½ times the height of Elbrus, and it falls short of “double” by
11 284 − 8848 = 2436 m
The truth in one picture: Everest's bar is nowhere near the red bar, which shows twice the height of Elbrus.
What went wrong in the infographic: the artist drew pretty mountain shapes instead of bars of equal width, and did not keep the base line and the scale honest. Once the picture stops obeying the scale, our eyes are fooled — we “read” a comparison that the numbers do not support.
Remember: a data picture may be beautiful, but it must first be true. Before you believe a fancy graphic, look for three things — does it start at zero, are the shapes of the same width, and is a scale given?