Ok I’ll take a shot at this. Im pretty sure the person sitting at seat number 3 would be Dalia (D). The reason is because the sum between Abby’s Chair and Colin’s chair must equal 6. There are only two number combinations that when added will equal 6 using numbers 1 to 5, and they are either (1,5) or (2,4). We know the sitting order Is Abby, Ben, Dalia, Sarah, and then Colin, so the possibility for Abby or Colin to be sitting in seat 2 or 4 is not possible because they are suppose to be seated together. So we now know Colin and Abby are in seats 5 and 1, now just follow the seating order and you will find the answer, Ben next to Abby, Dalia next to Ben, and Sarah between Dalia and Colin. Seat number 3 belongs to Dalia. I’ve included an image if it makes it better.