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