The sum of the 20 terms of an arithmetic sequence is 160. If the last term is -30, what is the first term?

I assume that you mean the 20th term is -30

Sn=n/2(a+L)

160=20/2(a+-30)

160=10(a-30)

16=a-30

46=a

a=46

The first term is 46

I have no checked you should though

 

 

 

Tn=a+(n-1)d

-30=46+19d

-76=19d

d=-4