Which of these numbers are in between 7.0 and 7.8?
It could have been more complicated than that but if we try the other answers, for example, 8.8 and add that to 7.2 and 7.6 and then divide by 3, the result will not be between 7.2 and 7.6.
Students have 3 hours so they can prove that the other anseers also do not work and find their answer.  2 points!!