Calculate s50 for the arithmetic sequence defined by (an)=(71-2.3n)

Answer 1

do it the same way I just showed you

Answer 2

I’m having trouble would I do a(50)=71-(2.3n)(50)

Answer 3

a(50)=71-(2.3n)(50)

doesn't even remotely resemble the formula I gave you.

What was your a ? What was your d ??