This is a unique game because we are given ordering information without specifics on the days in which to assign the variables, as in we are not told that the days start on Monday. Yet, through counting the variables - 5 hired on their own day and 2 pairs hired on the same day - we can deduce that there are 7 days total. Though we don't necessarily know that the first day starts on Monday, we can then use the ordering chain we made to place the variables in order. In other words, we may not know that the variable assigned to the first spot is on Monday, but we don't need to know that - we just need to know that it is assigned to be before the other variables. After reading our rules, we can deduce the following setup:
(FI/H) (H/FI) (D) (E) (B) (J) (CG)
Notice how there are no days of the week assigned to the above order. This question tells us that E was hired on a Monday. If this is the case, we know that the earliest B could have been hired is the following day- which would be a Tuesday, the earliest J could have been hired is the day after that- a Wednesday, and the earliest C and G could have been hired is the next day - a Thursday. We can make this deduction based purely off the relation of the variables to each other.
Does that make sense? Please let us know if you have any other questions!