Finding the sum of the first term and common difference when given sum of first 5 and sum of first 10 the sum of the first 5 terms of an arithmetic series is 110 and the sum of the first 10 terms is 320. How do i go about finding the first term and common difference.
Sn  = n/2 [2a+d(n−1)] is the equation for working out the sum of an arithmetic series, but how can i rearrange to find for the first term and common difference. I belive it would be using simulatenous equations.

Sn = n/2 (2a + (n-1) d)
110 = 5/2 (2a+(5–1)d) (Eq. 1)
320=10/2(2a+(10–1)d (Eq.2)
110=2.5(2a+5d-1d) - 110=2.5(2a+4d) (Eq.3)
320=5(2a+10d-1d) - 320=5(2a+9d) (Eq.4)
64=(2a+9d) - Divided both sides 5 from equation 4 (eq.5)
44=2a+4d - Divided both sides 2.5 from equation 3 (eq.6)
20=5d  - Simulataneous Equations - just minus it through. 64–44 is 20. 2a-2a is 0 and  9d-4d is 5d
4=d -20/5 is 4 
Sub d into equation (5)
64 = 2a+9(4)
64=2a+36
28=2a
14=a
Therefore the first term would be 14 and the common difference would be 4
