Question

а8 - а6 = 6______S10=155____a1=?____d=?

Answer 1

a1+7d-a1-5d=6
2d=6
d=3

155=2a1+(10-1)*3/ 2 * 10 
31=2a1+27
2a1=31-27
2a1=4
a1=4/2
a1=2