Question

What is the 20th term in the arithmetic sequence 200, 190, 180 ...

Answer 1

See you have here: \[a_{n} = 210-10n\]
substituting n = 20, well have
\[a_{20} = 220 - 10(20)\]
\[a_{20} = 220 - 200 = 20\]

Answer 2

The sequence function is: -10 (n-21)
-10(20-21)=-10(-1)=10

Answer 3

Subtract 10 until you reach the 20th term in the sequence :/ (lot plainer said that those guys ^ lol)