Determining the number of peaks is all about symmetry. The chemical environments are similar but not exactly the same - lets take W for example...
(It's a bit annoying that it's a ring, it make it harder to explain in text.) It has a plane of symmetry between the two NO2 groups, cutting the molecule in half. You have three carbons on each side, one carbon is directly attached to the NO2 this is one environment, the next carbon along is further away from the nitro group (environment number 2) and the last is even further away (environment 3). So you predict it to have 3 peaks.