Find a(subscript 6) of an arithmetic sequ3nce if a(subscript 4)=5 and a(subscript 9)=20.
The value of an increases 15/5 = 3 per term. Therefore
a4 = 5
a5 = 8
a6 = 11
a7 = 14
a8 = 17
19 = 20
The last term in my previous post should have been labeled a9, not 19.