What is a if numbers a+2,17,2a+2 are in arithmetic progression?

You need
to use the following properties of consecutive terms of an arithmetic progression
`a_(n-1),a_n,a_(n+1)` , such that:

`a_n =...

href="https://en.wikipedia.org/wiki/Arithmetic_progression">https://en.wikipedia.org/wiki/Arithmetic_progression