Use your formulas
a+9d = 34 (#1)
(20/2)[2a + 19d] = 710
2a + 19d = 71 (#2)
solve the two equations.
I would use #1 as a = 34-9d and sub into #2
Let me know what you got.
The sum of members of a arithmetic progression is:
a1-first number in arithmetic progression
d-common difference of successive members
n-numbers of members
In this case:
n=20 , (n/2)=10 , n-1=19
10d=30 Divided with 10
So members of that Arithmetic progression is:
For more information about Arithmetic progression go to wikipedia and type"Arithmetic progression"
Becouse nth member in arithmetic progression is: