Exercise 1 solution

t = N^2 / 2^EV_used, with N = 4, metered EV 12.
No compensation: 16 / 4096 = 1/256 s.
+1 EV: EV used = 11, t = 16 / 2048 = 1/128 s (standard speed 1/125).
-2 EV: EV used = 14, t = 16 / 16384 = 1/1024 s (nearest standard speeds in Chapter 1's list: 1/1000).
The sign convention (positive compensation means longer time in aperture priority) matches the article's statement that positive values add exposure; check it on a real camera.