The sequence formed by the number of members in the group for each year is
40, 46, 54, 64
This is a quadratic sequence because the second difference between consecutive terms is a common number.
Difference between 40 and 46 is 6
Difference between 46 and 54 is 8
Difference between 54 and 64 is 10
We can see that the common difference between 6, 8 and 10 is 2. This means that the difference between the number of band members in 2017 and 2018 is 10 + 2 = 12
Therefore, the number of band members is 2018 is
64 + 12 = 76
