Hello,
Well, there are many possibilities...
- the numbers are odd, so 28 is the wrong term
- the numbers are in an increasing order, so 28 is the wrong term
- the sum of the numbers is <10, so 28 is the wrong term
- the one I prefer : they are all multiples of 7, so 215 is the wrong term
And another one :
- I don't know what term to choose, and I don't want to bother, so is the wrong term