This game works through elimination. Remember that vertically the assignments cannot be the same as well as horizontally the assignments cannot be the same. To see this game in action take question 20 for example.
If one set of line 2 tickets is green that set will have to be the set in February. No more February tickets can be green so the green tickets for line 3 will need to be in January. That forces the red tickets in January onto line 1. Since line 1 tickets in February cannot be red, they will have to be yellow, forcing red tickets into line 3 for February.