Answer: 17 -3n
Explanation:
In the given arithmetic progression 20,17,14,11,8....
first term that is a = 20
common difference that is d= a2-a1 = 17-20 = -3
let n is the nth term
= a+(n-1)d
substituting the values of first, common,difference and n
=20+(n-1) (-3)
= 20 -3n+3
=23 -3n